ram 110. Sheath 105 terminates in a flat annular surface 115 at its front end and a flat annular surface 120 at its rear end. Front surface 115 is disposed at an inclined angle (approximately 30 degrees) relative to the longitudinal axis of sheath 105, so that the sheath is effectively sharply pointed at its front end. Rear surface 120 is disposed at an angle substantially perpendicular to the longitudinal axis of sheath 105. Sheath 105 has an axial bore 125 extending between its front surface 115 and its rear surface 120, and a straight slot 130 extending rearwardly from the tool's front surface 115 and terminating in a rear surface 135. Sheath 105 also includes a pair of rigid finger grips 140 which extend radially outward fromthe body tissue by pushing plunger 110 forward until the plunger's head section 155 engages the rear surface 120 of the sheath. As this occurs, the leading end 160 of the plunger engages the rearmost portion of the head 15 and propels the fastener head forward out of the sheath and into tissue 200. Tool 100 typically retreats slightly under this action, leaving an opening in the tissue to accomodate the fastener's head. The resilient nature of the fastener thereupon causes the fastener to try to straighten on itself, i.e., to cause head 15 to assume its original right angle position relative to filament 10. This straightening or restoring action causes the sharply pointed ends of the fastener's head to dig into the surrounding tissue as the head