What is the protective panel under the car door?
4 Answers
The plastic protective panel under the car door is called a side skirt. The side skirt refers to the skirt panels installed on both sides of the vehicle body, and its function is equivalent to an air dam, used to reduce the airflow entering the underside of the vehicle from both sides. It has a certain spoiler effect and can significantly reduce air resistance under certain conditions. Common door accessories include: Door glass: Provides the driver with a certain degree of side visibility, aiding in driving. Door hinges: Used to support the door, ensuring smooth opening and closing. Door handles: The interior handle is generally fixed on the door trim panel, while the exterior handle is fixed on the door outer panel, facilitating the closing and opening of the door.
I've been repairing cars for over 20 years, and that thing under the door is called a rocker panel guard – definitely not a small component. Its main function is to protect the vehicle's underbody, preventing stones, mud, and rainwater from entering the door and frame. Typically made of plastic or metal, it withstands scrapes and even helps reduce wind resistance for better stability at highway speeds. Many owners overlook it until they scrape a curb and it gets deformed. Left unrepaired, this accelerates chassis rusting, potentially costing hundreds to replace later. I recommend checking it every six months, especially in rainy areas where debris can clog drainage holes – give it extra scrubbing during car washes. I remember one case where a customer complained their door wouldn't close; turned out the deformed guard was jamming it, and everything worked fine after repair.
I've been driving my own car for over five years, and the protective panel under the door has required careful attention. It's called the rocker panel or side skirt, which usually protects against flying stones and prevents road mud from splashing onto the door trim. Last month, I accidentally scraped it against a curb, causing a crack. Fortunately, I got it repainted at the shop in time to avoid more serious damage. These panels come in various materials—plastic ones are lightweight but prone to cracking, while metal ones are more durable but can rust. I always remember to clean underneath when washing my car because accumulated leaves and debris can attract ants and block drainage holes. Prolonged moisture can accelerate corrosion on the lower part of the door, so it's something to watch out for during maintenance. Replacing a new one isn't too expensive, but it needs to match the car model and color, and sometimes you have to wait for the parts.
In our dealership, the under-door protective panel—commonly known as the sill guard—has quite a few common issues. It protects the underbody structure from water corrosion and foreign object intrusion, but it’s prone to damage if owners aren’t careful. For example, driving on snowy roads in winter exposes the metal guard to corrosive road salts, which can lead to rust spreading to door seams. We’ve repaired many cases and found plastic versions to be more durable, though they become brittle with age. Replacement isn’t costly—around 300–500 RMB for parts and labor—but don’t let minor issues escalate. We recommend regular rust inhibitor sprays and avoiding high-pressure car washes, which can strip paint. Some models feature aerodynamic designs; damage here may affect fuel efficiency. Minor scratches can be patched, but severe deformation calls for full replacement.
