If a skier is down, what signal should be used?

When a skier is down, holding a ski up serves as a clear and visible signal for assistance. This action effectively indicates to other skiers, instructors, or patrollers that the person is in need of help. The raised ski can be more noticeable from a distance, especially in a crowded ski area, helping to quickly draw attention to the situation.

In contrast, other signals such as hands over head or right hand out may not convey urgency or the specific situation as effectively, while a thumbs down could be interpreted in various ways and might not clearly indicate that someone requires immediate help. Therefore, holding a ski up is the most appropriate and recognized signal for indicating that a skier is down and needs assistance.