A manually operated staple gun includes a frame, a staple magazine, and a user-actuated unit. The user-actuated unit is mounted in the frame to switch between a first condition wherein the magazine is configured to guide staples of a first width along a guide axis into a ready position to be driven into a work piece and a second condition wherein the magazine is configured to guide staples of a second width along the guide axis into the ready position to be driven into a work piece.