A skid plate (sometimes called a sump guard) is a steel plate affixed to the underside of a vehicle to prevent damage to key components in the undercarriage. Skid plates are most frequently found on four-wheel drive vehicles designed for off-road use. Without protection, components such as the transfer case, oil pan and gas tank could be struck and damaged by rough terrain features on an off-road trail. Today, skid plates are often part of the off-road upgrade packages for trucks and SUVs offered by major automotive companies such as GM's Z71, Ford's FX4 or Toyota's TRD off-road package. They can also be purchased as an after-market upgrade from a variety of off-road outfitters.
It is also used on street application for lowered vehicles to prevent the same damages as on off-road application. The skid plate is mainly used as a protection to prevent the oil pan from grinding on speed bumps and boardwalks.