A side ridge line 13 of {TAIL ~ the blade portion} 12b forms {HEAD ~ a cutting edge} 
A side ridge line 13 of { TAIL ~ the blade portion } 12b forms { HEAD ~ a cutting edge }
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD