{HEAD ~ The combination} of the front perimeter edge and the seating axis define {TAIL ~ a front seating area} while the combination of the seating axis and the rear perimeter edge define a rear seating area 
define
{ HEAD ~ The combination } of the front perimeter edge and the seating axis define { TAIL ~ a front seating area } while the combination of the seating axis and the rear perimeter edge define a rear seating area
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH