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