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