the plungers engage the rearmost portions of the fastener heads and force them forward, thereby propelling the fasteners out of the sheath and into the tissue. Tool 400 typically retreats slightly under this action, leaving openings in the tissue to accomodate the fastener's heads. The resilient nature of the fastener thereupon causes the fastener to try to straighten on itself in the manner of fastener 5 described above, whereby the sharply pointed ends 327 and 329 of the fastener's heads 315 and 316 will dig into the surrounding tissue as the heads attempt to resume their normal position substantially perpendicular to the adjoining filament 310.

Due to the fact that the holes formed in the tissue by the retreating tool 400 are significantly smaller in diameter than the lengthat its front end and a flat surface 720 at its rear end. Front surface 715 is disposed at an inclined angle (approximately 30 degrees) relative to the longitudinal axis of sheath 705, so that the sheath is effectively sharply pointed at its front end. Rear surface 720 is disposed at a right angle to the longitudinal axis of sheath 705. Sheath 705 has an axial bore 725 extending between its front surface 715 and its rear surface 720 and two diametrically aligned slots 730 and 736 that intersect the axial bore. Slot 730 extends rearward from the sheath's front surface 715 and terminates in a rear surface 735. Slot 736 extends rearward from a front surface 737 and terminates in a rear surface 738. Sheath 705 also