A system, a closure, and method of use for determining the position of a blood vessel via a percutaneous puncture and for sealing the percutaneous puncture in the blood vessel. The system includes an introducer sheath and associated positioning device, a hemostatic puncture closure, and a deployment instrument. The positioning device enables the introducer sheath to be positioned at a desired position within the vessel. The deployment instrument includes a tubular carrier storing the closure. The carrier has a distally located free end to be extended via an introducer through the puncture and its associated tract. The closure comprises a radiopaque rigid anchor, a compressed collagen plug, and a thin filament connecting the two in a pulley-like arrangement. The carrier ejects the anchor through the introducer and puncture and then draws it against the free end of the introducer. The instrument and introducer are then withdrawn together to pull the anchor against the tissue contiguous with the puncture inside the artery. Further withdrawl draws the plug out of the carrier into the puncture tract, whereupon the plug moves with respect to the anchor into engagement with the outside of artery wall to seal the puncture or incision. A tensioning device limits the force applied to the filament. The carrier also includes a tamper which is used to mechanically deform the plug within the tract. Once positioned hemostasis occurs rapidly, thereby locking the closure in place.