Elongated {HEAD ~ tub} 16 has {TAIL ~ a pair} of upstanding sidewalls 18, 20 and a pair of upstanding end walls 22, 24 
Elongated { HEAD ~ tub } 16 has { TAIL ~ a pair } of upstanding sidewalls 18 , 20 and a pair of upstanding end walls 22 , 24
OTH HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH