Have you tried to repair a damaged tank?

Have you ever tried to repair any damage to your tanks, that would have caused it for not be filled without any repair (glass crack, frame issues, silicone problems, or even the brace breaking and causing for the tank to bow)? If you have, can you share you experience and what exactly was wrong with the tank, since I think dependent on the issue, many believe that it's not possible without a bunch of experience (or at all). I can't tell you how many tanks that I see being tossed in the trash, posted online for free, etc. that are damaged and are a unique tank design (or a tank that isn't sold anymore from the manufacture).