The temple endpiece is rotated relative to {TAIL ~ the lens} to set {HEAD ~ the pantoscopic angle} 
The temple endpiece is rotated relative to { TAIL ~ the lens } to set { HEAD ~ the pantoscopic angle }
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD