First just get four unsharpened pencils adn about 6-7 ruberbands. Use four of the rubberbands to attach them together as shown on the picture with the two pencils connected. Then, make a "T" with the pencils and attach them together with another rubberband. Last, use one rubberband and put each end into the notches in each end of the "T". Now its ready for firing. This is optional but if you want to put like a binder clip/clothes pin as a triggering mechanism at the bottom of the "T" to hold the rubberband in a firing position.