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