weight cost of shipping and cost of manufacture but provides significantly less grip and strength fig1 a 17c are perspective views of an u201c extruded u201d solid mounting rail 30 e with mounting clamps 28 a 28 b attached fig1 a being a close up of fig1 b fig1 c is an end on profile view of this same mounting rail 30 e one advantage of this type of mounting rail 30 e is its ability to accommodate different sized mounting clamp assemblies 28 a 28 b this allows the user to attach u201c light duty u201d accessories to a u201c heavy duty u201d mounting rail 30 e full sized mounting clamp assembly 28 a clamps over the entire rail 30 e while small mounting clamp 28 b assembly clamps over the upper edge of the mounting rail 30 e and a lower groove 148 in the face of the mounting rail 30 e while small mounting clamp assembly 28 b clamps over an upper groove 150 in the face of the mounting rail 30 e and the lower edge of the mounting rail 30 e fig1 a 18b and 19 a 19 b are perspective views of the upper mounting clamp cover 2 showing two different methods of fastening accessories slider rails to the upper mounting clamp cover 2 fig1 a and 18b show front and back views whereby standard bolts 2701 2704 are screwed into threaded holes in the upper mounting clamp cover 2 bolt 3003 shows how the bolt tip must not protrude past being flush with the inner face 3005 of the upper mounting clamp cover 2 so as not to inhibit the sliding of the cam action the advantage.