So me and my friends used to cut the bottom and top off a can with a screwdriver and hammer. You get four cans and tape them together so you end up with a hollow tube. You don’t cut the bottom of very lowest can off. On the bottom can you punch a hole in the side about 3/8 from the bottom and fill it with lighter fluid. Viola! Tennis ball cannon! You jam a tennis ball down the top and light the lighter fluid. If you are careful, you can make a cannon that will shoot a tennis ball straight up so high that it almost goes out of sight. We made our own slingshots too with a wire hanger, a pair of pliers, rubber bands and a piece of stiff cloth or leather to put the rock (or BB ) in.
