TimberTech® is focused on fasteners. Opt for the best fastening systems to install your deck. Cortex® Plug is a hidden fastener works with a system featuring a high quality, ACQ-approved, specialty deck screw with a Torx® tap® drive system. Included color-matched plugs are made from TimberTech® PRO® Reserve Collection deck boards to hide the fastener. It can be used on the entire deck surface, including stairs and perimeters, where other hidden fasteners cannot. Installation requires pre-drilling with a 7/32 in. drill bit.