As described, the testing apparatus rod and {HEAD ~ mandrel} threads into and pulls on {TAIL ~ the expander member} of the ribbed plug 
pulls on
As described , the testing apparatus rod and { HEAD ~ mandrel } threads into and pulls on { TAIL ~ the expander member } of the ribbed plug
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH