How to make a pencil launching crossbow with junk

Make a crossbow that launches pencils clear across the room.
This was made of different things from around the house. He was trying to see if he could make a crossbow with only household junk.

This crossbow works very well and a few things are adjustable, the pens and the strength of the pull and the power of it.

Also it is really easy to do it, so easy one can do it with one hand. Yes, I broke my arm a third of the way into the project, so I made it as easy as possible to build with one arm.

Hope whoever builds one will enjoy. And don't abuse the information.