This guy shows you how to make your own climbing holds from a Bondo Fiberglass resin and sand mix poured into clay molds. A customer at my old gear shop tried making some holds out of Bondo once and it didn’t work too well. His holds looked like someone had bolted a fossilized horse turd to the wall, and then they disintegrated after a few weeks. The do-in-yourself steps on Instructibles claims the sand/Bondo mix will add longevity to the holds, and the process of making them actually looks kind of fun. Try to find a well-ventilated area for mixing the Bondo or it might get a little too fun.

via Instructables