https://www.jpcorry.com/jp-corry-products/woodgrain-composite-deck-edge-board/
Woodgrain Composite Deck - Edge Board
Description
Putting the finishing touches to your composite decking is just as important as establishing a solid base Our edge board makes it easy to create a professional finish. Because composite decking has grooves along the edge for easy installation, you used to have to settle for either a grooved edge or a corner trim to cover the groove.