Originally Posted by mimiandrews
I'll pass along a tip I got from an old aircraft mechanic a long time ago. It is one I've never tried, but I was told it works sometimes.
Let the trailer (or airplane) sit in the hot summer sun until the metal is really hot, then touch a piece of dry ice to the dent. The sudden cooling might pop the dent out.
From what I have read, that doesn't work. But if you do decide to try it make sure to wear gloves or else you will get immediate frost bite...not a pretty picture.