An instrument, a closure, and method of use for sealing an opening, e.g., a percutaneous incision or puncture, in a living being. The instrument includes a tubular carrier storing the closure. The carrier has a distally located free end to be extended through the opening. The closure comprises an anchoring portion, a sealing portion and a thin filament connected therebetween. The instrument is operated to eject the anchoring portion of the closure through the incision or puncture and to then draw that portion against the free end of the carrier. The instrument is then withdrawn to pull the anchoring portion of the closure against the tissue contiguous with the incision or puncture. Further withdrawing of the instrument draws the sealing portion of the closure out of the carrier, whereupon it moves with respect to the anchoring portion and into engagement with the tissue contiguous with the opening on the opposite side of the anchoring portion to seal it. Signals are produced to indicate proper operation.