Each of the side surfaces has {HEAD ~ an inset} spanning from the block top surface to {TAIL ~ the block bottom surface} 
spanning to
Each of the side surfaces has { HEAD ~ an inset } spanning from the block top surface to { TAIL ~ the block bottom surface }
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL