Likewise, the seal could be made against the head of the plug instead of on {HEAD ~ the face} of {TAIL ~ the tubesheet} 
Likewise , the seal could be made against the head of the plug instead of on { HEAD ~ the face } of { TAIL ~ the tubesheet }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL