Abstract: A hammer-operated stapling apparatus which is characterized by a spring-loaded plunger having a staple drive plate that slidably extends between a front head and a back head to sequentially contact staples seated in a staple magazine attached to the back head. The staple magazine is closed by a pivoting cover fitted with a removable spacer and includes removable staple rails for accommodating staples of various size, which staple rails are fitted with a sliding follower biased against the staple string or cartridge by a follower spring seated on the staple rail. A handle is mounted to the front head and back head assembly and typically includes a hand guard for safely positioning the ends of the front head and back head on a wire or other element to be stapled to a post or board and facilitating striking of the plunger by the hammer to drive a staple into the board or post and secure the wire or element in place.