{HEAD ~ The blocks} of the invention comprise back {TAIL ~ legs} which are directed outwardly from the blocks back surface 
comprise
{ HEAD ~ The blocks } of the invention comprise back { TAIL ~ legs } which are directed outwardly from the blocks back surface
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH