Replace worn trailer bunks before they damage your gelcoat, as you shake, rattle, and roll down the road. Replacing Trailer Bunk Covers. … The common polypropylene carpet material that covers most trailer bunks serves two primary purposes: a smooth surface for the hull to slide on when launching and loading the boat, and protection for the hull when the boat is supported by the trailer, in storage, or being towed. We also offer Caliper OEM TRAILER BUNK WRAPS FOR PONTOON/ TRITOONS that are long lasting, highly durable, permanent solution, improving loading and unloading your boat, and saves wear and tear on your boat, trailer as well as your wench.