Abstract: Method and apparatus for interpolating elevation values and related locations from data provided on drawings by using an instrument with a supporting scale bar on which are mounted two slides that each has an extension arm. In use, the slides are set at the elevation values of the points on the drawing and one of the slides is moved along the scale bar intersecting a graphic scale at various intervals. The movable arm on the slide intersects the line joining the points on the drawing at various intervals.

Abstract: An adjustable carpenter square for use in determining the relative angles between two predetermined points defined by a pair of longitudinal extensions pivotally attached together at one end.

Abstract: An extensible rule and protractor formed by an equally dimensioned pair of superposed strap members, having indicia thereon, secured together by a screw projecting through one member and sidably received by a longitudinal slot in the other member. Guide pins, on one member entering longitudinal grooves on the other member, maintain the members in longitudinal alignment when one member is sidably moved longitudinally relative to the other. A circular groove intersecting the longitudinal grooves at one end portion slidably receive the pins permitting angular rotation of one member with respect to the other to measure and define a selected angular position.

Abstract: A computational aid device for Ekelund range determinations comprising a e member adapted to be placed over a bearing/time plot and including two leg members to be aligned with intersecting bearing rate lines faired through the plot, and a range scale positionable with respect to the base and the leg members to provide direct readings of range and of probable limits of range error.

Abstract: A device for determining the mean cardiac axis for aiding in the interpretation of an electrocardiograph includes a disc shaped member having a pair of radially extending arms pivotally attached to the center of the disc. The disc also carries a plurality of radial line markings thereon and preferably spaced every fifteen degrees. At least two of the radial markings, the one at 0.degree. and the one at 120.degree. representing the first and third EKG leads, have millimeter graduations thereon. Each arm has an elongated slide thereon which when positioned at the proper magnitude setting along the proper radial marking intersects the other slide to indicate the cardiac axis.

Abstract: A carpentry measuring tool including two arms pivotally connected at adjoining ends thereof. The two arms are angularly adjustable with respect to one another, and are adapted for determining the angle formed between the interior portions of intersecting horizontal and vertical surfaces of a door or window frame. One of the arms is provided with an extendable slide portion on the end thereof and is adapted for measuring the distance between interior portions of opposed surfaces of the frame. The distal end of the slide portion contains a spring biased heel which may be retracted for removal of the one arm from within the door or window jam. The angular relationship of the two arms and the length of the one arm may be fixed so that these measurements may be transferred to a door or window which is to be hung in a measured door or window frame.