To prevent leakage of gas from within the cell the substrates have {TAIL ~ sealing areas} 24 at opposite edges to cooperate with the sealing surfaces on {HEAD ~ the plates} 
To prevent leakage of gas from within the cell the substrates have { TAIL ~ sealing areas } 24 at opposite edges to cooperate with the sealing surfaces on { HEAD ~ the plates }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD