They are rather simple. They are made of a one piece, flat aluminum, black anodized, 0.011" thick, 1.260" wide metal. Outside length is 37-15/16", width is 16-3/4". There are 18 recessd mounting holes pre- drilled, a little less than 3/16" dia. The holes are positioned 1/3 of the distance (1.260")from the inside edge and are spaced around the perimeter every 5-1/4", there are 2 holes in the end lengths and 7 on the top/bottom sides. There is a cut seam on one end central in the height. The corners are rounded on a 3" radius.