{TAIL ~ The cavity} has {HEAD ~ generally vertical side walls} 13 and 14, end walls 15 and 16 and a generally rectangular floor 17 
{ TAIL ~ The cavity } has { HEAD ~ generally vertical side walls } 13 and 14 , end walls 15 and 16 and a generally rectangular floor 17
TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH