A woman discovered a dent in her car and took it to a repair shop. The repairman decided to have a bit of fun. He told her to simply drive the car home and blow into the tailpipe until the dent popped out.
After fifteen minutes of trying, a friend came by and asked what she was doing.
"I'm trying to pop out this dent, but it's not working," the woman explained.
Her friend replied, "Duh, you have to roll up the windows first!"