Abstract: A closure device for sealing a percutaneous puncture in the wall of a blood vessel, duct, or lumen of a living being. The puncture has opening in the wall of the blood vessel, duct, or lumen, and a tract contiguous therewith. The closure device is arranged to be inserted into the puncture by an introducing instrument and basically comprises an anchor, a collagen plug, a flexible filament, and locking disk. The anchor is arranged to be brought into engagement with the interior tissue of the vessel, duct, or lumen contiguous with the opening, while the plug and the locking disk are located within the tract. The filament is arranged to be pulled to apply tension thereto. While tension is applied to the filament the locking disk and the plug are moved in the tract toward the anchor. The filament comprises an engagement loop, a first extending portion, and a second extending portion. The engagement loop is coupled to the locking disk.