Long story short doing paintless dent repair on car door dents from other people opening there door and slamming into another car door.
I use to roll the car window down slide a piece of card board between the glass and the outer door skin and remove the dent without taking the door panel off and using the glass as a back up for my tool. Takes on a normal door dent about 2 minutes to remove the dent. Made good money in the old days and saved the customer lots of money. Been doing it for 40 years but now lost my touch, I can't see and focus anymore and the the new door glass is not as strong.