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