A panel for attachment to a mounting surface includes a plurality of raised faces formed and extending between an upper edge and a lower edge of the panel, and a plurality of recessed keyways defined between each of the raised faces. The panel may have a recessed base at the lower edge of the keyways defining a fold lip adjacent the mounting surface, and a full base formed at the lower edge of the raised faces and extending beyond the recessed base. The fold lip provides a reaction point for an under lap extending from the lower edge toward the upper edge. The panel may include a lock flange formed at the upper edge. The lock flange defines a lock slot between layers of the panel, and closes the lock slot to substantially zero depth at a first touch point and a second touch point.