The sidewalls 57 typically define an obtuse angle with {HEAD ~ the bottom surface} 55 of {TAIL ~ the recess} 53 
of
The sidewalls 57 typically define an obtuse angle with { HEAD ~ the bottom surface } 55 of { TAIL ~ the recess } 53
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH