{HEAD ~ Key way} 4 opens to {TAIL ~ its front end} at front face 6 of housing 2 and is blind or closed at opposite end 7 of housing 2 
{ HEAD ~ Key way } 4 opens to { TAIL ~ its front end } at front face 6 of housing 2 and is blind or closed at opposite end 7 of housing 2
HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH