The Poolform liner is a flexible rubber insert that is grooved at the top so it will lock firmly into the back piece. The form liner is interchangeable to give you a selection of different edge profiles and textures to tie in with your hardscape design: square, bullnose, bullnose slate, bullnose travertine, bermuda (french curve), chiseled stone, and chiseled slate. These popular textured edges match most deck stamps on the market and eliminate extra work to create a seamless appearance.