Abstract: An apparatus for retaining a circuit board in a connected position is constituted with a top cover and a U-shaped retention body. The top cover has pivoting features disposed at one end and locking features disposed at the other end. The U-shaped retention body has a base and a cavity disposed therein, and two arms rising from each side end. The rising arms include receiving features correspondingly disposed on their top ends. The top cover pivoting features mate with one the receiving features to allow the top cover to pivot at one of the top ends, placing the apparatus in an open position for inserting the circuit board into the cavity, and in a closed position, with the locking features mating with the other receiving feature, securing the inserted circuit board.

Abstract: A lead-in guide and starting locator for use with a sheet metal card guide or similar structure is disclosed. The disclosed lead-in guide is preferably of a one piece construction and is most preferably molded or machined from a plastic material. The lead-in guide of the present invention provides multiple board lead-in slots and preferably includes integral retention pegs for quick mechanical attachment or can be held in place by a separate fastener. In a preferred embodiment, the lead-in guide has a top surface cut by a series of grooves that will be aligned with the slots in the card guide. Preferably, the lead-in guide has a front section that is somewhat thicker than the rest of the lead-in guide.

Abstract: The invention concerns a carrier arrangement (10) comprising a longitudinal column-type carrier (15), whereby a coupling arrangement is provided to establish a mechanical and simultaneously electrical connection to a medical apparatus (40). The coupling arrangement comprises two guide rails (20, 30) which are electrically insulated against each other and extend along the entire length of the carrier (15).

Abstract: A device for attaching and detaching a mounting board unit with respect to a device body in a substantially vertical posture includes a controller base which has a detachable mounting board fixed thereto and a guide portion engaging a guide rail provided on the device body. The guide portion guides the controller base when the mounting board unit is attached to and detached from the device body. Mounting boards having different shapes can be mounted on the unit of the same construction, and even a mounting board on which a heavy device such as a hard disk is mounted can be easily attached to and detached from the device body in a vertically arranged condition.

Abstract: The present invention provides an assembly of a first panel formed with at least one insertion notch extending inwardly from at least one panel edge and a second panel carrying at least one projecting tab extending outwardly of at least one of its edge and fitting in one of the notches. The tab has on at least one of its sides a shoulder defining an edge which is located along the projecting length of the tab at a position intermediate the free edge of the tab and its base, which usually coincides with the edge of the panel from which it projects. The shoulder edge is in abutting contact with a region of the first panel adjacent the insertion notch in the first panel in which the tab fits and functions to maintain the associated edge of the second panel out of contact with the first panel so that the relative positions of the panels is determined by such abutting contact and is independent of other factors, such as the precise linearity of the panel edge.

Abstract: The present invention provides an assembly of a first panel formed with at least one insertion slot and a second panel carrying at least one projecting tab extending outwardly of at least one of its edges and fitting in the slot. The tab has on at least one of its sides a shoulder defining an edge which is located along the projecting length of the tab at a position intermediate the free edge of the tab and its base. The shoulder edge is in abutting contact with a region of the first panel adjacent one of the insertion slot and thus maintains the associated edge of the second panel out of contact with the first panel so that the relative positions of the panels is determined by such abutting contact. The first and second panels can be positively secured together by means of an interconnection element, preferably in the form of an integral flange bent up from one of the panels, which is attached to one or both other panel by screws, bolts and nuts or similar attachment devices.

Abstract: A circuit card retainer for securing a circuit card within a circuit card receiving channel to mitigate the possibility of a circuit card connector jarring loose from a motherboard slot during transit or other vibration or shock causing activity. The circuit card retainer securely retains an inner edge of the circuit card upon insertion of the circuit card, and allows the circuit card to be extracted only if the groove abutment is flexed away from the inner edge of the circuit card, thereby removing the obstruction caused by the groove abutment.

Abstract: The collapsible housing frame has a pair of side frame boards opposed to each other, and connecting mechanisms which connect both the opposed ends of the side frame boards. Both ends of the side frame boards are connected to the connecting mechanisms through first hinges. Each of the connecting mechanisms is formed to be collapsible at a second hinge of the connecting mechanism, and a lock-unlock system to lock and unlock the hinge is provided at the second hinge.

Abstract: An instrument chassis is disclosed. The chassis includes a housing with a front opening in a first loading plane, and instrument receiving slots located in the housing. These slots are engageable to printed circuit cards inserted through the front opening. The chassis also includes first and second power supplies. The first power supply is electrically coupled to a first set of instrument receiving slots, and the second power supply is electrically coupled to a second set of the instrument receiving slots. Thus a first set of the printed circuit cards may maintain electrical and mechanical separation and isolation from a second set of the printed circuit cards.

Abstract: An extracting device for plug-in modules having a holding bracket for securing a front plate as well as a printed circuit board to a profile rail of a module rack. A pivoted lever is articulated to a holding bracket; the pivoted lever rests with a pressing shoulder against a front face of the profile rail. To facilitate the extraction and to accomplish a large extraction lift, the pivoted lever is displaceable with respect to the holding bracket with the aid of a sliding mechanism which has a sliding pin on the holding bracket and a sliding track on the pivoted lever whose swing pin is displaceable in a slot of the holding bracket.

Abstract: A computer chassis with a mother board and at least one slot opening in the back of the chassis and a daughter board attached to the chassis by a bulkhead. The bulkhead is slid into the slot opening in a self-aligning manner until the daughter board is mated to an electrical connector on the mother board. The bulkhead fits snugly into the slot opening due to side and bottom flaps on the bulkhead and wedge shaped springs on the sides of the slot opening. The top of the computer housing contains a feature to capture and hold a top edge of the daughter board against movement. The top of the computer housing also contains an EMI liner and spring clips that correspond to the top edge of the bulkhead and secures the bulkhead in the computer housing, thus providing consistent and improved EMI/RFI containment.

Abstract: An electric receptacle assembly including a flat base plate and a cover shell, wherein the flat base plate has two upright partition boards, two rows of upright metal frames respectively extended outwards from the upright partition boards, a circuit board supported between the partition boards, two pairs of metal contact plates fastened to respective bevel slots on the upright metal frames and connected to the circuit board by conductors, two metal contact rods respectively connected to the circuit board for connection to power supply, and two ground conductors respectively connected to the circuit board; the cover shell has two sets of plug holes on two bevel bearing surfaces at two opposite sides thereof corresponding to the metal contact plates for mounting electric plugs.

Abstract: A box-shaped rack forming an electronic device housing has a plurality of guide grooves for guiding upper and lower edges of electronic circuit packages. A plurality of dummy surface plates are pivotably mounted on a front opening portion of the rack and arranged side by side. Each dummy surface plate is biased by a spring, so that when the electronic circuit package is not inserted in the rack, the dummy surface plate is kept in abutment against the inner surface of the rack to shield a part of the front opening portion of the rack. When the electronic circuit package is inserted into the rack, the dummy surface plate is pushed by the electronic circuit package to pivot inward of the rack, and is finally replaced in position by the package surface plate mounted on the electronic circuit package. When the electronic circuit package is removed from the rack, the dummy surface plate is reversely pivoted to restore an original position and again shield the part of the front opening portion of the rack.

Abstract: A robust optoelectronic transceiver module which is quick, easy, and inexpensive to manufacture. The transceiver module has a main housing which consists of a potting box with potting material inserted therein. In addition, a circuit board is encased by the potting material. The circuit board has an optical subassembly mounted thereon. The optical subassembly extends outside of the potting box through a recess. Correspondingly, a recess cover is provided for forming a liquid fight seal between the recess cover, the potting box, and the optical subassembly.

Abstract: A housing designed to accommodate a plurality of removable electrical devices includes power connectors mounted within the housing for connecting a power source to each of the devices. In order to prevent a user from inadvertently contacting live connectors within the housing, the housing is provided with one or more safety elements e.g., in the form of fins fixed in the cavity which are positioned to lie between adjacent devices. The position, size and location of the pins are strategically chosen to prevent access to the connector(s). The position of the fins between the devices allows the user access to the devices to load and unload them into and from the housing.

Abstract: The present invention provides, in a computer chassis containing a substantially planar removable expansion card therein, the computer chassis having an opening therein allowing access to the expansion card, a plane of the expansion card substantially parallel with a plane of the opening, a support structure for the expansion card and a method of supporting the expansion card.

Abstract: A printed PWBA guide member 30 in which a card guide 22 and a slide 14 with a slot 34 for receiving a PWBA 10 are all integrated for ease of installation and alignment of the card guide 22 with a card connector 18 residing on the PWBA 10.

Abstract: A shelf assembly which has realized an easy mounting of a back wiring board to a shelf. The shelf assembly comprises a shelf including a cross beam connecting a pair of side walls on a rear side thereof; and a back-board mounting frame including a pair of side plates each having a vertical guide groove, a first upper connection member and a second upper connection member for connecting the side plates, a first intermediate connection member and a second intermediate connection member for connecting the side plates, and a lower connection member for connecting the side plates. The shelf assembly further comprises a back wiring board inserted into the back-board mounting frame from above along the guide grooves formed in the side plates; and fixing means for fixing the back-board mounting frame to the shelf.

Abstract: An outdoor wireless base station with a circuit pack within a housing. A printed circuit board of the pack has opposite edges formed with spaced projections and the housing has spaced guide elements to receive the projections for mounting purposes. To mount the circuit pack, the circuit board is moved to pass the projections laterally between the guide elements to enable the projections to become aligned with and then to move along the guide elements.

Abstract: A card cage for mounting circuit boards comprises lateral panels and an electrically connecting panel extending between the lateral panels. Opposed sets of two spaced rails span the lateral panels and support extruded grille units substantially transverse to the connector panel and the lateral panels to define a cavity for receiving the circuit boards. A plurality of guides formed integrally with each grille unit receive edges of circuit boards inserted in the cavity. Each set of rails and associated grille units define a grille structure of the card cage. A method for forming a grille structure for use in a card cage comprises the steps of forming a support member and support rails. Forming the support member includes extruding a metal piece with a planar portion and a plurality of elongated, U-shaped members carried by the planar portion, cutting the metal piece transverse to the U-shaped members and forming a connecting surface.

Abstract: This is a data card frame provided with a unique end rail which is bifurcated to form a receptacle port which can accept any number of different connector headers each of which is designed not only to mate with a selected external plug or terminal but is further uniquely designed to mate with a particular data card being supported in the frame. The receptacle port in the frame is also provided with locking detents coded to assure the correct positioning of the connector header in the receptacle port during insertion therein. The receptacle port is further provided with metal latching inserts matching locking hooks on a mating external plug that permit the external plug to be inserted into, with minimal force and securely latched thereto.

Abstract: An electronic equipment drawer 20 is aligned with an electrical connector in a tunnel in the horizontal and vertical directions with alignment pins and holes. A screw drive 34 and cam 36 mounted on the drawer engages a tunnel wall and controls insertion into the tunnel to provide proper electrical contact and lock the drawer in place in the tunnel. A bus extender card 25 inserted in a connector 26 centrally located on a mother board 21 is supported by surfaces on a bar 28 extending between end walls 24 of the drawer. The end walls 24 include pairs of channels 31 on opposed walls which support feature cards inserted into connectors mounted on the bus extender card 25.

Abstract: An assembly is provided for uniformly applying pressure to a selected portion of a circuit board mounted between spaced surfaces. The assembly includes a retainer for selectively applying pressure to a proximal surface of the circuit board and a stiff U-shaped bar having a channel in which the retainer is mounted, the bar thus being interposed between the retainer and the circuit board. Preferably, the retainer includes at least one member that is attached to the bar by a snap-in fit. When the retainer is actuated, the bar is pressed against the circuit board, thereby causing the opposite surface of the circuit board to uniformly press against a housing slot wall. A side wall of the bar preferably contacts a wall of a slot in which the assembly is mounted to enhance heat transfer.

Abstract: A guide mechanism prevents an improperly oriented PC card from being inserted a significant distance into a PC slot. A pair of PC card guide mechanisms are coupled to a PC male connector. A PC card is received at the guides as the card is inserted and pushed toward the male connector. Each guide mechanism includes a proximal end that engages an edge of the male connector, and a distal flanged end that receives the PC card. A guide rail extends between the proximal and distal ends of each guide mechanism. At least one guide mechanism includes a flexible arm along its guide rail. At the tip of the arm is a keying mechanism responsive to the PC card orientation. When the PC card is properly oriented, the card slides over the keying mechanism pushing it aside to traverse the guide rail. When the PC card is improperly oriented, the card is blocked by the keying mechanism so as not to traverse the guide rail.

Abstract: A memory card which includes a circuit substrate having a generally planar surface, comprises a frame with an opening in one of a top or a bottom wall thereof for receiving the circuit substrate. A support structure on the frame supports the circuit substrate within the card. A cover closes the opening and encloses the circuit substrate and the electrical component within the internal card space created by the frame and cover. The support structure of the frame includes a plurality of shelves at different vertical locations within the frame to support the circuit substrate at different vertical levels to accommodate varying heights of electrical components mounted on one or both surfaces of the substrate. The circuit substrate includes a peripheral edge area with cutouts corresponding to only one of the shelves whereby only the periphery of the substrate need be modified for locating and supporting the circuit substrate at different levels within the card.

Abstract: Interior circuit card supports and a method that facilitate fast and simple Assembly and disassembly of the circuit cards, and provide both interior and peripheral card support, are disclosed. A plurality of circuit cards 32a-32n, each having at least one interior hole 36, are positioned substantially parallel to each other with the holes of the various cards collinear. A plurality of grommets 38 are secured in the holes, with each grommet providing a first coupling. A rod 42 having a plurality of second couplings 44 is inserted through the grommets such that the second couplings mate with the grommets' first couplings to provide an interior support that maintains the spacing between the circuit cards. In the preferred embodiment the grommets are internally threaded with a groove that extends their entire length, and the rod has deformable inserts that form an interference fit with the grommets' threads. The rod is inserted and then rotated, causing the inserts to deform and grip the threads.

Abstract: A connector system for an add in PC card for supplying network communications functions to a host computer wherein the connector to the network is a RJ type universal jack consisting of a socket and plug. A cavity in the card is formed by an opening in the short dimension of the frame opposite the 68 position connector and the top and bottom covers. A carriage is mounted in the cavity so that it can slide in and out and occupy at least two positions. The carriage consists of a socket portion for making contact with the RJ type plug and a support and contact portion that mechanically supports the carriage within the card and also makes the electrical contact between the carriage and the card. In the first of the two positions, substantially all of the carriage is within the cavity. In the second of the two positions, the socket portion of the carriage is outside of the cavity. In this position, the socket is electrically connected to the printed circuit board.

Abstract: An electronic package that is tested before the leads of the package are cut and bent into a final shape. The electronic package has a plurality of leads that extend from an outer housing of the package. The package is typically rectangular in shape and has a group of leads extending from each side of the housing. Extending along each group of leads is a strip of dielectric material that is spaced an offset distance from the side of the housing. The package is tested by placing a plurality of corresponding test pins into contact with the leads over their final cut and formed length in an area between the housing and the dielectric strip. The area of contact corresponds to the ends of the final assembled leads, so that the actual impedance of the leads over their final cut and formed length are tested. The dielectric strip provides structural support for the leads during the handling and testing of the package.

Abstract: A supportive guide for circuit-card grounding comprises a conductive strip (40) attached to a base of an elongated track (50) that has a U-shaped cross-section defining a longitudinal slot (52) and staggered protrusions (68,70) located at the proximal end of the trak. The strip contains a plurality of spring contacts (42) protruding into the slot via a plurality of openings (60), formed in the base of the track. Snap-in posts anchor the base of the track to a chassis (84) such that the conductive strip is sandwiched therebetween.

Abstract: A function expanding apparatus for a compact electronic device includes a casing having a supporting portion and a supporting plate attached to the casing to be movable in a predetermined direction. A pair of retaining portions are formed on the supporting plate. The rear portion of the electronic device is mounted on the supporting portion and is positioned in its width direction by a pair of positioning members provided at the supporting portion. The front end portion of the electronic device is mounted on the supporting plate and the retaining portions engage the front edge of the electronic device so as to restrain the movement of the electronic device in the depth direction thereof. The position of the retaining portion is adjusted by moving the supporting plate, in accordance with the depth of the mounted electronic device.

Abstract: A printed circuit board mounting apparatus for securing a printed circuit board within a chassis includes a track affixable to the chassis and a locking mechanism affixable to the printed circuit board. The track, which includes a plurality of locking points, is slidably received within the locking mechanism, which engages the track at any of the several locking points to secure the track within the locking mechanism. The mounting apparatus described herein enables the chassis to accommodate printed circuit boards of different sizes without mechanical modification of the chassis.

Abstract: A direct connection for printed circuit boards where a primary board has a slot therethrough with slight edge projections which control the width of the slot to close tolerances. Spaced parallel conductive strips on the surfaces of the primary board terminate at the slot. A secondary board has an insert portion sized and configured for insertion into the slot in a close fit with the edge projections to maintain the boards mutually perpendicular. Spaced parallel strips on the insert are disposed adjacent the termination of the primary board strip. The strips are interconnected by soldering to provide direct circuit interconnection between the primary and secondary boards.

Abstract: A mounting bracket is disclosed that is intended to be used, in conjunction with other identical mounting brackets, to facilitate the insertion and removal of certain printed circuit boards known as AT style cards into and out of passive backplane or motherboard slots in a computer housing, as well as to protect the AT style computer cards from damage while they are resident in the housing. The mounting bracket of the present invention is adaptable to fit an AT style card of any length, and is capable of providing close spacing between inserted cards.

Abstract: The invention concerns a microelectronic device having body (42) and abutment device (46, 47, 48) projecting from one face of the body (42) for abutment of the microelectronic device to a support member (62), the body (42) including an electrically active region (41) with a sensitive axis (51), characterised in that the abutment device (46, 47, 48) has a predetermined relationship with the sensitive axis (51) to thereby enable alignment of the sensitive axis (51) with an expected signal axis.

Abstract: An assembly for mounting a circuit board between spaced surfaces is disclosed. The assembly includes a housing and a circuit board retainer including a protrusion. The housing is designed and constructed to receive and retain a fully assembled circuit board retainer. The housing includes at least one pair of channel walls defining a channel for receiving an end of the protrusion. The channel walls are constructed to permit movement of the protrusion into and out of the housing when a force in a proper direction above a predetermined threshold is applied to the protrusion.

Abstract: A rack comprises a plurality of lower guide rails arranged side by side to form the bottom thereof, and a plurality of upper guide rails arranged side by side to form the top thereo, for accommodating a plurality of electronic modules such as modems. Each of the modules includes a rectangular casing, lower and upper side edges of which are rounded or chamfered. The lower and upper guide rails are in vertical register with each other, respectively, and are vertically spaced from each other by a distance corresponding to a vertical height of the case. Each of the lower and upper guide rails has a pair of ridges coextended in parallel with each other and defining therebetween a guide path for complementarily and slidably receiving the corresponding side of the casing, whereby an outer width of the guide rails can be generally equal to a thickness of the casing due to the rounded or chamfered sides thereof.

Abstract: An avionics line replaceable unit (LRU), of the type having numerous electronic circuit cards disposed therein in a parallel fashion. The cards being securely held in place when the cover of the LRU is screwed on thereby actuating a spring which transfers force to the circuit cards.

Abstract: Within an electronic shelf, physically separating or isolating in a front to rear direction keying elements from connector alignment elements to provide a separation distance, minimizes the undesirable interaction that may occur between keying elements and connector alignment elements due to tolerance effects. Worst case manufacturing tolerances with respect to keying elements, for example, no longer influence in any significant way, the co-action of the connector alignment elements. Insertion of circuit packs into respective receiving stations is achieved with less effort since effort is not required to overcome extra frictional forces resulting from the keying elements interacting with the connector alignment elements.

Abstract: An electrical installation device for fastening in an attachment position on a carrier rail includes an instrument housing made of insulating plastic and having an instrument housing wall and a bottom facing the carrier rail in an attachment position. A sliding latch is shaped in one piece to the instrument housing wall and is movable in a locking direction outside of the housing bottom transversely to the attachment direction and to the carrier rail direction. A flexible web, spring elastic in the locking direction, is connected between the sliding latch and the instrument housing wall. A detent lug is attached to the sliding latch and, in the locking direction, grips behind the carrier rail. An actuating end is connected to the flexible web and faces away from the detent lug, whereby the sliding latch is returnable against the spring elasticity of the flexible web from a locked position into a release position by actuation of the actuating end.

Abstract: The invention is directed to a coding device for electrical assemblies that can be inserted parallel to one another into a module frame and that are contacted via plug devices attached at the back to a wiring backplane.A coding flange having three quadratic openings arranged in a right angle pattern is arranged on the wiring backplane between the guard rails, and a corresponding coding housing likewise provided with three quadratic openings arranged in a right angle pattern is arranged on the assembly next to the plug connector. Coding pins can be selectively oriented within the openings by 90.degree. turns, whereby the free ends of said coding pins are fashioned as tongues having a rectangular cross-section, and the area of the cross-section of the tongues corresponds to half the area of the cross-section of the quadratic openings.

Abstract: A printed circuit board mounting box includes a casing covered with a top cover, and two reversible end plates vertically disposed at two opposite ends between the top cover and casing thereof, wherein each end plate has parallel rows of horizontal T-rods at one side at different elevations for mounting printed circuit boards inside the rectangular casing horizontally; each T-rod has two grooves for mounting printed circuit boards inside the casing vertically.

Abstract: An adapter for supporting e number of printed wiring cards onto an electronic equipment rack equipped with means of support for cards of a larger size. The adapter includes end plates mentioned to fit into the mounting hardware of an existing rack normally providing space for larger cards. The end plates and sides being virtually identical to the older type and size of printed wiring card.

Abstract: A card file adapter assembly for mounting a plurality printed wiring cards of a smaller size than are normally permitted on an associated electronic equipment mounting rack. The adapter is so constructed in size as to be able to be slid directly into existing mounting hardware of an older type providing mounting space for printed wiring cards of a more reduced size.

Abstract: A cooling system for a plurality of circuit boards, each circuit board having a substantially planar thermally conductive thermal sink having longitudinal sides and being in thermal contact with a plurality of electronic components dissipating heat, includes a heat exchanger for delivering heat to a cooling medium and a heat pipe for transferring heat from each thermal sink to the heat exchanger. The heat pipe includes at least one flat box-shaped heat pipe, at least a first part of the heat pipe being in thermal contact with the longitudinal sides of the thermal sinks of the circuit boards.

Abstract: A sheet metal support cage structure within a computer has an inturned side wall ledge portion and removably receives a spaced series of expansion cards. Extending along edge portions of the cards that face the ledge are sheet metal mounting brackets having outwardly bent end tab portions that overlie and engage the side wall ledge. The tabs are removably held in place on the ledge by an elongated hold-down bar secured at an inner end thereof to the cage structure for pivotal movement relative thereto between a closed position in which the bar overlies the tabs and captively retains them on the ledge, thereby locking the expansion cards in place within the cage structure, and an opened position in which the bar is moved away from the tabs and releases them from the ledge to permit the expansion cards to be removed from the cage structure.

Abstract: A telecommunications closure (1) includes a pressure clamp (21) for sealingly clamping mating parts (47, 48) of the closure together so as to form a water tight seal. The clamp member requires no tools during installation and creates no uncertainty as to the generation of appropriate clamp pressure on a sealing O-ring when installed. The pressure clamp includes an over-center latch which is rotatable between a first unlatched position and a second latched position, a clamping pressure generated by the latch increasing to a maximum value as the rotatable latch is moved from its first position to an intermediate position between the first and second positions and then decreases from this maximum value as the latch is moved from the intermediate position to the second position so as to generate a predetermined appropriate clamping pressure when in its second position so as to appropriately compress the O-ring disposed within a groove between the closure parts at their mating area.

Abstract: The present invention relates to fastening elements for guide rails at the support rails of a component carrier which is provided to accommodate printed circuit boards equipped with electrical components. The fastening elements are configured as U-shaped spring bars and include a fixed U leg attached to the underside of the guide rails and a free, resilient U leg which is oriented toward the longitudinal web of the support rails. The resilient U leg permits easy insertion of the guide rails into the support rails. The dimensions are such that, after insertion of the guide rails, the resilient U leg stands on the longitudinal web and thus the guide rails are tightly locked against being pulled out.

Abstract: A card cage for housing a plurality of circuit boards and passive optical fiber couplers contains a tray for storing express optical fibers or express optical fiber tubes not to be coupled within the card cage but rather expressly routed through a distribution point accommodating the card cage. The tray has a flexible hinge thereon and means for keeping the tray passively deflected away from the optical couplers for facilitating insertion and removal of optical fibers into and from the couplers. A card cage housing snap fits to a card cage base without requiring screws or other physically detachable elements. The housing also includes a plurality of flexible deflectable clips integrally molded as part of the card cage housing which normally keep the circuit cards or boards within the card cage housing but which are deflectable so as to allow the boards to be slideably inserted and removed from channels within the housing for guiding the boards.