A blonde woman was driving her car home one night when she suddenly found herself in the middle of a really bad hail storm. The hail stones were as big as golf balls and her car gets dented up really bad. The next day she takes it in to a repair shop to have the dents looked at.
The repair guy noticing that she is blonde and quite dingy when she speaks, decides to have some fun and tells her to blow into the tail pipe of the car really hard when she gets home, and that doing this will cause all of the dents to pop out.
When she gets home she starts blowing into the tail pipe as hard as she can, over and over. Just then, her best friend who also is blonde shows up. Her friend sees her blowing into the tail pipe and is quite startled by the action. She blurts out all flippantly, "What are you doing!?"
She tells her the repair guy told her to blow into the tail pipe real hard and the dents would pop out.
Her girlfriend says "Duh! You need to roll up the windows first!"