An extrusion for receiving and interconnecting laminated panel sections for quick construction of partitions or enclosures is disclosed. The extrusions form frame members for the partitions or enclosures and are designed to permit quick assembly and disassembly of building structures without the use of fasteners. The extrusions include channel portions adapted to receive the edges of the panels, the panels being grooved and adapted to snap into the corresponding channels. The extrusions may be H-shaped in cross section for forming panels into a flat partition or wall, may be formed with a channel on one side and adapted to receive door or window fittings on the other side, or may be formed in a corner unit configuration to permit joining of panels at right angles. The corner unit extrusion includes two interlocking half members which define a central cavity for receiving a rigid pipe, which prevents the interlocking members from being separated. The extrusions and panel sections are particularly adapted for use in constructing light-weight truck canopies, and for this purpose J-shaped interlocking extrusions permit quick connection of side panels to a roof panel and form a pivotal hinge for an access door.