{HEAD ~ The recesses} 16′ have {TAIL ~ at least one wall} 20′ extending from the associated base 12′ 
have
{ HEAD ~ The recesses } 16′ have { TAIL ~ at least one wall } 20′ extending from the associated base 12′
HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH