{TAIL ~ The top ply} has a wall formed therein which interlocks with {HEAD ~ the bottom ply wall} to cover and close the well 
{ TAIL ~ The top ply } has a wall formed therein which interlocks with { HEAD ~ the bottom ply wall } to cover and close the well
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH