an end portion 118 of each outer tube is flattened and one bracket 116 is fastened to the flattened end portion by a rivet 120 the other bracket 117 is fastened to the end of the rod 110 by a rivet 122 the outer ends of the brackets 116 on the diagonal braces are bent into a rounded configuration to form a cylindrical sleeve 124 at the end of each bracket 116 each sleeve 124 carries an outwardly projecting shaft 106 having a cylindrically curved outer surface the shaft is held in the sleeve by a spring pin 128 at the opposite end of each diagonal brace the outer end of the bracket 117 is bent into a rounded configuration to form a cylindrical sleeve 130 at the end of the bracket each sleeve 130 carries an outwardly projecting shaft 132 having a cylindrically curved outer surface and the shaft is held in the sleeve by a spring pin 134 the brackets at the ends of the diagonal stabilizing braces are secured to hubs at the corners of the bottom cubicles of the frame as described previously the inside face of each hub has a bore to receive cross braces extending between front and back planes of the expanded framework for holding the front and rear faces of the framework in a fixed position relative to.