{HEAD ~ Recess} 42 in {TAIL ~ turn} comprises channels 44 and open portion 46 
in
{ HEAD ~ Recess } 42 in { TAIL ~ turn } comprises channels 44 and open portion 46
HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH