Toe-in is the turning-in of the wheels, while toe-out is the turning-out of the wheels from the geometric centerline/thrust line. The purpose of toe is to ensure parallel rolling of the wheels. Toe also serves to offset the small deflections of the wheel support system which occur whenever the vehicle is rolling forward. Even when the wheels are set to toe-in or toe-out, the wheels tend to roll parallel on the road when the vehicle is moving.