Also, the testing apparatus uses {HEAD ~ the rotation} of a threaded rod to apply {TAIL ~ the force} necessary to create the face seal 
to apply
Also , the testing apparatus uses { HEAD ~ the rotation } of a threaded rod to apply { TAIL ~ the force } necessary to create the face seal
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH