Abstract: Apparatus for fabricating three-dimensional structures for children is provided in which four-way, three-way and elbow fittings having opposing flat sides with orthogonally oriented sockets are used to interconnect cut-to-length tubular members. An end portion of a tubular member is connected to an end portion of a socket by a fastener having a pair of spring loaded opposing pins thereon. The fastener is positioned in a tubular member with its opposing pins protruding out of diametrically opposing holes on the end portion thereof. The end of a tubular member is inserted with a slip fit into a socket until it contacts an internal shoulder thereon and is then rotated until the opposing pins snap into diametrically opposing holes on the end portion of the socket.

Abstract: A light weight, portable, gymnastic assembly made for children to climb on is fabricated of tubular members formed of cut-to-length standard plastic tubings and standard plastic fittings. The tubular members are releasably held within the sockets of the fittings by pairs of opposing spring-loaded pins that are carried in opposing holes on the end portions of the tubular members and engage within opposing holes on the end portions of sockets of the fittings when the tubular members are slipped into the sockets. Because of the mechanical connections used, such an assembly provides a flexible overall structure that can be readily modified from time-to-time by an adult to enable a number of separately assembled different types of accessories of interest to children to be mounted on the surface of the assembly or within the interior thereof.