Blue rocks top the swirling water backdrop with the Boulder Swirl pattern. Overlap liners are designed to fold over the top of your pool wall and do not require a bead receiver. Overlap liners are held in place with coping. Be sure to check the measurements of your swimming pool to assure the correct size is purchased. Pool height is determined by measuring the outside wall from the ground to underneath the top rail. Oval pool size is determined by measuring from the center point across the longest and widest ends.