Wall 31 has formed therein a hole 32 bounded by {HEAD ~ a circumferential margin} 33 provided by {TAIL ~ wall} 31 
provided by
Wall 31 has formed therein a hole 32 bounded by { HEAD ~ a circumferential margin } 33 provided by { TAIL ~ wall } 31
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL OTH