{HEAD ~ The block} generally comprises {TAIL ~ a front surface} 12 and a back surface 18 adjoined by first and second side surfaces 14 and 16, respectively, as well as a top surface 10 and a bottom surface 8 each lying adjacent said front 12, back 18, and first 14 and second 16 side surfaces 
generally comprises
{ HEAD ~ The block } generally comprises { TAIL ~ a front surface } 12 and a back surface 18 adjoined by first and second side surfaces 14 and 16 , respectively , as well as a top surface 10 and a bottom surface 8 each lying adjacent said front 12 , back 18 , and first 14 and second 16 side surfaces
HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH