Toe-in is the turning in of the wheels from the geometric centerline/thrust line. Toe-out is the turning out of the wheels from the geometric centerline/thrust line. The purpose of toe is to ensure the parallel rolling of the wheels. Also, toe serves to offset the small deflections of the wheel support system which occur when 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.