Abstract: A kit of contructural elements permitting the quick assembly and knockdown of a temporary building structure. The kit includes a plurality of base beams which form the base frame of the structure. The two ends of each base beam are opposingly stepped whereby adjacent base beams can form an overlap joint at each base corner. Aligned apertures are formed through the overlap joint. Beneath each step at the end of a beam there is provided an undercut, whereby at a corner the undercuts merge to provide a notched corner. An upright stud with a depending bolt is inserted into the aligned joint and projects into the notch whereby a nut can fit onto the bolt without lifting the frame. The single nut is used to interconnect a vertical stud and two adjacent horizontal beams. Upper beams are utilized at the roof level and also include stepped corners. Wall panels can be inserted into grooves formed in the various beams and studs.