{HEAD ~ The block back legs} may extend in {TAIL ~ a plane} parallel to the block front surface or extend forwardly toward the blocks front surface 
extend in
{ HEAD ~ The block back legs } may extend in { TAIL ~ a plane } parallel to the block front surface or extend forwardly toward the blocks front surface
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH