{TAIL ~ An undercut groove} 323 is formed in {HEAD ~ the transverse side wall} 321 b 
{ TAIL ~ An undercut groove } 323 is formed in { HEAD ~ the transverse side wall } 321 b
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH