{HEAD ~ The undercut groove} 323 extends from the second end surface 312 b to {TAIL ~ the vertical notch surface} 318 b 
extends to
{ HEAD ~ The undercut groove } 323 extends from the second end surface 312 b to { TAIL ~ the vertical notch surface } 318 b
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH