The insert has two arms that each extend from the intersection of {HEAD ~ imaginary extensions} of {TAIL ~ the secondary locating sides} 
of
The insert has two arms that each extend from the intersection of { HEAD ~ imaginary extensions } of { TAIL ~ the secondary locating sides }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL