Once hollow closed end needle 10 has been inserted into place in flexible closed end sheath 4 stopper 26 is slid over hollow closed end needle 10 in {HEAD ~ the direction} of {TAIL ~ button} 25 until teeth 27 and 28 grip around cylindrical surface 31 of element 32 a of button 25 
of
Once hollow closed end needle 10 has been inserted into place in flexible closed end sheath 4 stopper 26 is slid over hollow closed end needle 10 in { HEAD ~ the direction } of { TAIL ~ button } 25 until teeth 27 and 28 grip around cylindrical surface 31 of element 32 a of button 25
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH