I am making a set of roto-chocks that are made entirely of aluminum and stainless steel. The clamping action is done by rotating a stainless steel nut on a piece of stainless allthread which is 1/2 inch in diameter. The upper and lower clamps are made of thick wall 2 inch aluminum square tubing that have a 20 degree angle cut at each end. These clamps are then fitted with stainless steel pressure pads which are 2 1/4 inch x 3 1/2 in. The pads are held in place by 3/8 inch stainless steel bolts which serve as axles so the pads can pivot slightly to achieve as much contact as possible. I would post a picture here later this afternoon if I could figure out how.
Dave Nowlin