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