A locking device will lock {HEAD ~ the tieback member} to the groove in {TAIL ~ the wellhead housing} 
A locking device will lock { HEAD ~ the tieback member } to the groove in { TAIL ~ the wellhead housing }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL