The gun is fed over the rivet's mandrel (a shaft protruding from the rivet head) and the rivet tail is inserted into the work. When the gun is actuated (typically by squeezing the handle), a ball on the rivet's tail is drawn towards the head, compressing a metal sleeve between the ball and the head. This forms another "head" on the opposing side to the workpiece, drawing the work together and holding it securely in place.