{HEAD ~ A cap} covers the open top and has {TAIL ~ a recessed surface} formed therein directed toward the open top 
{ HEAD ~ A cap } covers the open top and has { TAIL ~ a recessed surface } formed therein directed toward the open top
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH