{HEAD ~ A high reflector} is affixed to {TAIL ~ the optics plate} and configured to receive the fourth reflected beam 
is affixed to
{ HEAD ~ A high reflector } is affixed to { TAIL ~ the optics plate } and configured to receive the fourth reflected beam
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH