{HEAD ~ An area} of contact between the sidewalls 57 of the recess 53 and the sidewalls 59 of the insert 21 can be along {TAIL ~ a line} or over an area where the angle of the recess sidewalls match the angle of the insert sidewalls 
along
{ HEAD ~ An area } of contact between the sidewalls 57 of the recess 53 and the sidewalls 59 of the insert 21 can be along { TAIL ~ a line } or over an area where the angle of the recess sidewalls match the angle of the insert sidewalls
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH