In the prior art, it has been customary for some time to utilize extruded aluminum tubing for construction purposes. The extruded aluminum forms the corner posts and horizontal bracing and support members utilized in various shelters. To support side walls between the various vertical and horizontal members, a special extrusion has been required which extrusion is riveted or otherwise secured to the tubular extrusion. Through the utilization of the special extrusion to receive the side walls of the unit, wasted material results and in addition, a special extrusion for each thickness of side wall is required. Such obviously results in added expense for tooling, inventory, handling and the like. In addition thereto, the typical fascia member utilized in the prior art is secured together at the mitered corners through the utilization of an angle bracket received in a specially extruded groove of each of the fascia members where they abut. The angle bracket is secured internally of each of the grooves. Such structure results in awkwardness during assembly as well as ill-fitting corners.