Here the o-ring material is being inserted (friction fit) into the channel. The o-ring material is .250" Buna-N 70 O-Ring Cord Stock, from theoringstore.com. The glue is Vibra-Tite 388 Super Glue (specifically for gluing rubber) from Amazon. I used the chisel to make clean out the channel and ensure it was fit to hold the o-ring. The reinforced area (extra later of fiberglass) alongside the long side of the lid is where two latches will be installed. Next up - build the lockers!