through openings 74 b in the collar 74 through the openings 71 j and into the annular depression 73 c each screw 74 a has a first end 74 a u2032 that abuts the annular depression 73 c of the ring 73 and a second end 74 a u2033 a nut 75 is coupled to the second end 71 d of the adaptor 71 and covers the coiled spring 72 the ring 73 and the collar 74 the nut 75 includes an outer surface 75 a an inner surface 75 b having threads 75 b u2032 and an opening 75 c a retaining ring 76 is located on the shaft 71 g behind the opening 75 c the nut 75 is coupled to the second end 71 d of the adaptor 71 via engagement between the threads 71 d u2032 75 b u2032 of the adaptor 71 and the inner surface 75 b of the nut 75 the adaptor assembly 70 is disposed on the attachment portion 62 of the mechanism 60 such that the first pin 71 e and the second pin 71 f are inserted into the first set of slots 62 a the adaptor assembly 70 is then rotated to insert the pins 71 e 71 f within the second set of slots 62 b and thereby couple the adaptor assembly 70 to the mechanism 60 at the same time that the adaptor assembly 70 is disposed on the attachment portion 62 the shaft 71 g and ring 73 are disposed over the guide wire 40 as shown in fig7 a upon rotation of the nut 75 the inner surface 75 b of the nut 75 abuts the collar 74 and causes the collar.