This is a diagram of what a ballista should look like. The materials you need to make one ballista are 2 small pulleys, binder twine, and staves. All you have to do is follow the diagram.
This is a picture of the begining of a ballista.
This is a picture of more work in progress.
This is a picture a ballista that is finished. It was the winner for 1998. Of course it was the cubscout patrol that was visiting us with the senior patrol leader who was helping them. Oh have I mentioned I was the Senior Patrol Leader when this event happened.