Fixing a dent or rust spot on a car instead? Wood filler isn't made for that job. See our step-by-step guide on how to use Bondo body filler for auto body repair. Bondo Wood Filler is a two-part filler for repairing damaged, rotted or missing wood on doors, windows, trim, fences and furniture. It sets fast, sands in about 15 minutes, and can be stained or painted, indoors or outdoors. This guide covers the right mix, how to apply it, and how to get a repair that blends into the wood. What You'll …