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