when you have a grass catcher that you no longer use? I guess if your into airguns you do something like this,hehe. Sorry that I didn't take pics of the build in progress, but you can get the idea and I am making 2 more, so I'll take more pics. I used a scrap piece of 3/4"MDF for the top and back. The bottom and sides are scrap 1/2" plywood. I put 2 pieces of 1x2 on the bottom and 1 piece for the top and sides to hold a piece of cardboard in place. The front piece on the bottom is drilled for golf tees, so I can splatter the target when it's done it's job. On the inside I used an old boat cushion, in the middle of the cushion was 2 pieces of thin, kinda mudflap material, that I used in front of the rest of the cushion. It works great only had a few pellets make it to the cushion in the back, none have made it through. The board on the top I let stick out about 6", seems to help keep the glare off of the target midday. I had an after thought, that it would have been better to use a wheeled garbage can, easier to move around.
Mike