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