The tub thus has sidewalls defining arm rests, end walls defining a foot rest and back rest, and {HEAD ~ a bottom} defining {TAIL ~ a seat} 
defining
The tub thus has sidewalls defining arm rests , end walls defining a foot rest and back rest , and { HEAD ~ a bottom } defining { TAIL ~ a seat }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL