{HEAD ~ Preferably one grid field} of the second grid structure fits onto several grid fields of {TAIL ~ the first grid structure} 
{ HEAD ~ Preferably one grid field } of the second grid structure fits onto several grid fields of { TAIL ~ the first grid structure }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL