The border between the sole and the hoof wall as seen on the solar view of the hoof. Usually colored pale yellow, as opposed to the water line which is normally white. Deterioration of the white line and/or inner hoof wall is called white line disease, seedy toe, and onychomycosis.

White border between sole and wall of horses.

white border between sole and wall of horse's

White Line (2003) is an album by Memorain.

a white stripe in the middle of a road to mark traffic lanes