therefore be possible or even preferable to use a sheath that is the same size as or even smaller than the previously removed procedure cannula with the front end 25 of sheath 45 held snugly against the wall of artery 11 plug 57 is slid down through lumen 27 of sheath 45 as shown in fig9 until it reaches end 25 of sheath 45 where it encounters artery 11 if an insertion apparatus like that shown in fig1 is used plug 57 is initially housed in plug holder 29 when it is time for plug insertion holder 29 is screwed onto sheath assembly 23 by means of threads 37 and 41 and piston 49 is inserted into channel 31 advancement of the piston then forces plug 57 from holder 29 into sheath 45 and through lumen 27 to the artery wall once resistance is felt the physician slowly withdraws the sheath while continuing to maintain pressure against the piston so that plug 57 remains pressed against artery 11 when shoulder 51 of knob 43 abuts rear end 53 of holder 29 the physician knows that plug 57 has been pushed entirely out of lumen 27 as shown in fig1 axial pressure is maintained for a short period of time perhaps as little as one minute or as long as five minutes depending upon the circumstances to allow plug 57 to seat in tissue channel 9 and against arterial puncture 13 minimal axial pressure is thereafter continued while clamping pressure is slowly released until a good self sustaining hemostatic seal has been confirmed the sheath holder and pusher can all then be removed while it is believed that the preferable procedure is to permit both piston and sheath to remain in place until a self sustaining hemostatic.