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