Made from a polyethylene foam 1/4" thick. It creates a barrier between the sand bottom and the swimming liner. Pool liner failure due to puncture is minimized and you get a smooth easy to clean bottom. Foam Pool Pad is easy to install. Roll out a section of pad on top of the sand along one side of inside the swimming pool after the wall is set-up and cut the foam pad. Next, seam enough sections together with duct tape to cover the dimension of the swimming pool. (optional, flip pad over so tape is facing the ground) Trim off excess pad material and you are ready to install the pool liner.