{HEAD ~ The edges} of the slots are lined with {TAIL ~ upstanding flanges} which are sharpened to form cutting edges 
are lined with
{ HEAD ~ The edges } of the slots are lined with { TAIL ~ upstanding flanges } which are sharpened to form cutting edges
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH