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