The block has two side extensions extended inward of {HEAD ~ the notches} of {TAIL ~ the base} 
of
The block has two side extensions extended inward of { HEAD ~ the notches } of { TAIL ~ the base }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL