Abstract: A clamping device is provided from which various structural systems can be built comprising poles or tubular members, panels or a combination of the same. The clamping device comprises a pair of socket-forming assemblies hinged for pivotal movement preferably about a common hinge axis which enables the socket axes to be progressively varied between positions where they are parallel to a selection of positions where they are perpendicular to one another. Means are provided for selectively locking the socket-forming assemblies in any one of their adjusted positions. Each of the socket-forming assemblies comprises a pair of confronting members having confronting surfaces forming a socket for receiving a panel or rubber-like insert member having a slot adapted to receive a panel therein. The socket-forming surfaces of each pair of confronting members terminate to form an entryway into the socket of appreciable size and preferably asymmetrically related to a line at right angles to the hinge axis.