2x2 1/2" plywood then a 2x2x 1/2" rubber pad . This comes in 4x6' sheets at ranch stores, for transporting sheep,etc in back of pickup. I used A 4x4 for in front of my wood lathe.Cut two 2x2 for backers. This one is like 10 years old.If the pellets start coming back at you,slap in a piece of carpet also. the 10 meter gun they stay in behind cardboard.....Pete
