The frame has {HEAD ~ a shallow rabbet} which extends from the nasal region of one eye rim, through the nasal region of the bridge, into the nasal region of the other eye rim, and has {TAIL ~ a predetermined depth} 
has
The frame has { HEAD ~ a shallow rabbet } which extends from the nasal region of one eye rim , through the nasal region of the bridge , into the nasal region of the other eye rim , and has { TAIL ~ a predetermined depth }
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL