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