It also has {HEAD ~ an end bar} of hafnium secured to the bottom plug by {TAIL ~ a purely mechanical connection} 
secured by
It also has { HEAD ~ an end bar } of hafnium secured to the bottom plug by { TAIL ~ a purely mechanical connection }
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL