I found an old jon boat in the back of someones yard - it was OLD! I got 2 sticks to go over all the rivets (after pounding them tighter) and there was a large 1/4" seam crack in the hull. I pounded it down as close as I could and used this stuff to go over it. I lightly sanded it down smooth then painted over it. That was 2 years ago, and I have yet to get a leak.