Strike Plate/brackets, bolt them on to the corners of the ST bed and the factory ST cover will have two slid pins that will slid/lock into the middle section of the bed. Once you slide the pins in the middle (one on each side) close the lids of the cover down and they should lock into the strike plate/brackets.
Like I said, in my prior post....I paid $30 for all four strike plates including the screws to mount them to the bedside.