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