Putties are liquids that fill gaps, holes, and crevices to heal surface damage and prevent leaks. They come in a variety of formulae for a variety of permanent and emergency repairs, including gap sealing in underwater applications and halting leaks in gas tanks, pipes, burst radiators, and pools. Wood and auto body surfaces can also be repaired with putties. After mixing, two-part epoxy putties start to set and can cure completely within minutes.