This design is meant to be a really cool rubber band launcher that is purely mechanical. To make something shoot, it always needs a trigger mechanism. A trigger is a tool that turns a little energy, in this case the turning of the clip around the body, into enough energy to launch the rubber band off the mechanism. What is especially funny is that the trigger mechanism is powered by another rubber band. There are 6 clips around the body, each one having loaded a rubber band and will subsequently fire each one as the clips rotate.