Back in my Northstar Automotive days we boiled 'em to get 'em back to shape, removes creases and all. Plus, you don't run the risk of melting it. Now, you ask, where the heck am I going to find a pot big enough to boil it in? You don't need to. With the cover removed and propped-up accordingly, poor boiling water into the dented corner and let it stand a few minutes, gently start pushing the dent out with the business end of a baseball bat or similar large rounded object. Put another pot on to boil while you're doing this so you can repeat the process. A large turkey cooker with propane burner works great for this. At Northstar we had large boil tanks but you can achieve the same results with the method described. Best of luck and DON'T SCALD YOURSELF!!!