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