I have pretty much this same backstop at my house. We bought a 1/2 inch thick piece of road steel from home depot (The stuff they use to cover holes in the road when they are working on them) Its about 4ft x 4ft, with a wooden frame and a wooden box to hold sand in it at the bottom. What I have learned from using it over the last two years is that you really need to re-enforce the slanted wood beams with steel. When the round hits the jacket shreds and flys into the wood uprights/supports, over time this sereously eats away at the wood. Additionally you have the same problem with the sand in the base. Rounds push the sand back from the rear of the trap, and you just end up putting all your rounds into the dirt under the trap. I will be re-enforcing the sides and base after I rebuild it from scratch this spring.