Slip-on rocker bottom, driver and passenger's side, fits the standard cab 1999-2006 Chevrolet Silverado2007 Classic Chevrolet Silverado1999-2006 GMC Sierra2007 Classic GMC SierraThe rocker panel is the piece of steel that is visible underneath the door when it is closed. Rocker panels are generally C shaped as you look at them from the cross view. They usually start at the pinch weld just underneath the vehicle and curve up and over onto the doorsill going toward the floor pan. This item is intended to be welded in to replace the rust damaged portion.