The arched notch 101 has a shape match with that of {HEAD ~ the curved back side} of {TAIL ~ the toothed arch block} 12 
of
The arched notch 101 has a shape match with that of { HEAD ~ the curved back side } of { TAIL ~ the toothed arch block } 12
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH