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