Bob, it is built in such a way that you can lay a 50 lb. cement block on it, it has two verticle hardwood posts 2x2 inches by about 16 inches tall as the front corners, the base is 12x24x1/4 with hardwood perimeter underneath, two 1/8x1 inch braces go from the rear bottom to the top of the front posts. Two 3/4 in by 3 in hardwood boards go across the upper front with various adjustable holes and slots, all 1/4 in bolts. I use a solid 10 inch cement block which probably weighs more than 50 lbs. The largest engine I've tested is a Mustang 50 and it was piece of cake.