You need 7 redstone,arrows ,7 blocks ,5 redstone torches, a lever, and a dispenser.first dig 1 block down. Put a redstone torch in and a dispenser over it. next put 2 blocks next to the dispenser and redstone torches in back of it. Put 2 blocks on top of those torches and 2 redstone torches in back of it. Then put 2 more blocks on top of those torches and put a block in the middle. Finally place redstone over all of those blocks besides on the dispenser. Lastly put a lever on the side and fill the dispenser with arrows. Sometimes it stops. just flip the lever back.