102 includes a similar step portion 109 also adapted to contact the plate members 22 122 gaskets 132 are provided within step portions 107 and 109 which serve to seal the plate members 22 122 against the clamp 100 clamp 100 further includes an aperture 110 having a threaded portion 111 adapted to engage the threads of fastener 106 the tubular member 102 also includes an extended portion 131 which also extends between the plate members 22 122 and is adapted to contact extended portion 130 of t member 101 in the operation of clamp 100 the apertures 104 110 of t section 101 and tubular member 102 respectively are aligned and a fastener 106 is inserted the fastener is tightened until the edge 120 of extended portion 130 of t section 101 and the edge 121 of extended portion 131 of tubular member 102 contact further compression is thereby prohibited the lengths of extended portion 130 and extended portion 131 are selected so that upon engagement via the rotation of fastener 106 gaskets 132 of step portions 107 109 engage the plate members 22 122 in a tight and compressive manner but do not compress it excessively thereby avoiding any damage to the plate members 22 122 in the manufacture of the panel assembly plate members 22 24 are molded using state of the art extrusion molding techniques each.