Blonde repairs

A blonde was driving home after a game and got caught in a really bad hailstorm. Her car was covered with dents, so the next day she took it to a repair shop. The owner saw that she was a blonde, so he decided to have some fun. He told her to go home and blow into the exhaust pipe really hard, and all the dents would pop out.

So the blonde went home, got down on her hands and knees and started blowing into her exhaust pipe. Nothing happened. So she blew a little harder, and still nothing happened. Her blonde roommate saw her and asked, "What are you doing?"

The first blonde told her how the repairman had instructed her to blow into the exhaust pipe in order to get all the dents to pop out. The roommate rolled her eyes and said,

"Uh, like hello! You need to roll up the windows first."