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