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