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