Cut the blunt end of the skewer so it is an appropriate length for the neck of the banjo. Then, wrap your rubber band around the bottle cap four or five times. The number is optional.
If you have extra rubber band like me, take the twist tie and wrap it around the base of the extra band. Insert the skewer piece under the wraps of rubber bands. Continue wrapping the twist tie all around the exposed skewer. You may want to put a piece of tape on the back to make sure nothing unravels.
You're done! Pluck those rubber band strings, and you're ready for a mini band!