Anatomical snuff box, also known as the radial fossa: a triangular depression on the dorsal-lateral aspect of the hand just distal to the wrist joint. The lateral boundary is formed by the parallel tendons of the extensor pollicis brevis and abductor pollicis longus, and the medial boundary by the extensor pollicis. Thus, since all three tendons can be easily palpated when these muscles contract, the fossa is best seen and felt when one extends and abducts the thumb.
The name refers to the use of this area for holding and then snorting snuff, a powdered tobacco concoction.
Anatomical snuff box in action