These are two pencil launchers that I just made. The instructions are for the second, which works WAY better. A ruler is the main part in this gun. A binder clip is the trigger, and the power is supplied by a rubber band. It is very simple to make, so just look at the pictures. The lego handle is optional. To shoot it, you put the pencil on the rubber band, and pull it back. Then, you put the end of the pencil (with the rubber band around it) into the clip and let it close. To fire, you just squeeze the clip, which lets go of the pencil and the rubber band, which forces the pencil forward, propelling it out of the gun. The tube at the end it to keep the pencil going straight until it leaves the gun, so its pretty much just a barrel. The first gun you see is the first one I made, and the second set of pictures are my most recent gun.