A rocker panel assembly for a vehicle includes an upper rocker panel, a lower rocker panel, and a fastener. The fastener connects the upper and lower rocker panels. The fastener has a frustoconical tip to locate the fastener on the lower rocker panel, a body with a plurality of fins to stabilize the fastener between the upper and lower rocker panels, and a shoulder including an arrow-head configured to clamp the lower rocker panel to the upper rocker panel between the shoulder and a head of the fastener.