A Yuhk Soo Doh is formed by compressing the fingers together, but unlike a Soo Doh the thumb is tucked into the palm. Impact is made with the inner ridge on the lateral (thumb) side of the hand. The technique is usually done in a horizontal motion (palm down), but some variations use an upward motion. Care is usually taken not to "lock" the arm at the elbow, to prevent hyperextension of this joint on impact. Executing this strike with a downward motion is only possible if the shoulder is rolled forward to allow the striking surface to point down. Due to vulnerable aspects of the inner ridge of the hand, this strike should only be used on highly sensitive pressure points or soft tissues of the body.