Abstract: A collapsible three sided truss, in which a rectangular central framework section has outboard framework sections each hinged to one side, which can be swung together to bring interfitting portions together, with locking mechanisms manually operable to connect these portions together and form a rigid three sided truss. When released and swung out, the outboard sections form a flattened array with the central section for easy transport and handling. Slidable pins are included in the locking mechanisms, engaging aligned holes in partial sleeves on cross members of one outboard section fit to elongated member of the other outboard section. The three sided trusses can be connected end-to-end with couplings and locking pins.