{HEAD ~ Mobile plaque}, without trapping, presents {TAIL ~ a target} difficult to maintain in contact 
{ HEAD ~ Mobile plaque } , without trapping , presents { TAIL ~ a target } difficult to maintain in contact
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH