How to distinguish radial ulna

The radius is the bone on the side of the thumb, and the ulna is the bone on the side of the little finger. The two bones are at the wrist joint, and the carpal joint is related. The radius is thicker and the ulna is thinner at the wrist. In the direction of the wrist joint and the elbow joint, the ulna gradually becomes thicker and smaller, while the radius becomes smaller and smaller. Then at the elbow joint position, the radius is the capitulum, and the ulna is the olecranon.