Ports 12, 12′, 12″ etc. shown here have {HEAD ~ primarily a structural function} for {TAIL ~ machine frame} 1  
for
Ports 12 , 12′ , 12″ etc . shown here have { HEAD ~ primarily a structural function } for { TAIL ~ machine frame } 1
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH