A staple gun tacker includes a wire guide mechanism in its forward end which includes a wire guide plate having a recessed lower end for engaging a wire when the plate is in an extended position and a rotatable cam for moving the plate between extended and retracted positions which includes a circular slot formed therein having one end thereof located closer to the axis of rotation of the cam then the other receiving and engaged with a projection on the cam plate so that rotation of the cam is translated into linear movement of the wire guide plate.