a deck plank is co - extruded from an extrusion die which receives molten plastics materials supplied from three separate plastic extruders to provide the plank with opposite sides having different colors . preferably , the base plank is extruded from a lower cost material such as reground scrap polyvinylchloride , and thin pvc cap layers are co - extruded on opposite sides of the base plank in different colors . opposite edges of each plank have longitudinally extending grooves for receiving hidden fasteners in the form of screws extending through short flat tie pieces or a continuous sealing tie strip projecting into the opposing grooves of adjacent planks .