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