These protect the area under the doors. The best ones have no protruding brackets underneath and are strong enough to bear the weight of the vehicle when it is sliding over rocks. They also provide the added benefit of a step, making access to a lifted 4×4 much easier.
Offroad driving exposes your vehicle to damage from various obstacles such as rocks, logs, bumps and scrapes, particularly prevalent in vehicles with low ride height or independent suspension.
Underbody protection plates are commonly relied upon offroad as a layer of armour underneath your 4×4 protecting key components.