Its called a lock-out, it goes close to the nose. On either side of the nose there are two screws. It goes on the side that has a slot between the metal plate and the plastic. Unscrew the two screws remove the plate it put the "z" and spring between plate and plastic housing. Put the two screws back. Now check to see the lock-out is being pushed up by the feeder when there are no nails in tool