{HEAD ~ The body} is open at {TAIL ~ a first or top end} and closed at a second or bottom end 
{ HEAD ~ The body } is open at { TAIL ~ a first or top end } and closed at a second or bottom end
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH