Abstract: A joint between a vertically oriented hollow section column (1) and a horizontal load-carrying beam (3) in a two-story building structure such as an exhibition stand, which can be rapidly erected and dismantled, includes a straight core (2) fitted into the upper end of the column (1). The quadratic hollow section core (2) has a projecting bolt head (21) at the middle of either side surface. Each side wall of the generally quadratic hollow section column (1) has a central, axial slot (12) on its inside. On its underside the beam carries a dependent guide body, the width of which corresponds to the width of the internal column slot and is guided by this slot. The short end of the beam (3) has a vertically directed Tee slot (32,36) extending upwardly from the central area of the beam for accommodating the head and a portion of the shank of the screw on the core (2).