The FastenMaster Collated Cortex Hidden Fastening System is the fastest, easiest way to hide fasteners in composite, cap stock, and PVC decking boards. Cortex offers a strong connection between the deck board and joist. It hides fasteners across the entire deck, first and last board, perimeter and stairs. Cortex plugs are made with the same material as leading deck boards, meaning you can achieve a perfect seamless finish across your whole deck.