Before and after: Repairing rotted wood on a window sill and boards. This sill had a swamp cooler which must have leaked. You could follow the path of the water right through all the rotten wood. Awww crap. Figured I'd spend the day scraping old paint and instead pulled off a window swamp heater to find a bunch of rot. The clapboard and window sill is completely rotted, and the bottom of the window frame is soft too. New window sill - maple and pine. I didn't have the time to take apart the whole window, so I chiseled the base back to the stable wood and screwed the new pieces into place. Second layer of epoxy, next up: sanding! Second layer of Bondo, sanded and ready to paint. Final Paint For the window sill, most of it was damaged and replacing it with some new wood was better than patching it back up. Wood epoxy (Bondo) seals and smooths large splits in the siding, and after some sanding and finish work it's back to new.