Referring to the example of FIG 5, the J slot 70 of {HEAD ~ the string} engaging means 26 are housed in {TAIL ~ a J slot sleeve} 136 which is fastened to the upper end 52 of mandrel 22 
Referring to the example of FIG 5 , the J slot 70 of { HEAD ~ the string } engaging means 26 are housed in { TAIL ~ a J slot sleeve } 136 which is fastened to the upper end 52 of mandrel 22
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH