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