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