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