Are you serious? It's a poor man car parking helper. You drive into the garage and aim to have the hanging tennis ball (hung from rafters) line up with your steering column to control your left and right spacing. And as soon as the glass touches the ball determines how far you have parked into the garage.
This keep the car away from the clothes washer and dryer up front and yet the car just foward enough that the garage door wont hit the back of the car.