Riven Prest® Brick replicates the look of stone with contoured sides and a face textured to simulate natural riven stone. Riven refers to the surface of flags, which is a natural bedding plane within the rock from which the flagstone is quarried. A natural riven surface is achieved by splitting blocks of stone, creating uneven surfaces with crevices and clefts. Because Riven Prest® Brick has a wider joint style, Polymeric Sand is recommended for joint filling.