The parking sensor holder is a plastic housing or bezel that secures the ultrasonic parking sensor into the vehicle’s bumper. While the sensor does the electronic work, this holder ensures the sensor sits flush with the bumper surface and is angled correctly to detect obstacles. These holders are often glued or clipped onto the inside of the bumper cover. If a car is involved in a minor fender bender, the holder often breaks, causing the expensive sensor to fall inside the bumper cavity.