Also, the block has the surface of {HEAD ~ arcuate shape} in {TAIL ~ cross section} at least at a part of its side surface 
in
Also , the block has the surface of { HEAD ~ arcuate shape } in { TAIL ~ cross section } at least at a part of its side surface
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH