Identify the depression found on the posterior surface of the humerus.

The Olecranon fossa. It is the large depression at the distal end of the humerus. The olecranon fossa of the humerus together with the olecranon process of the ulna permit full extension of the forearm. The two depression is the olecranon fossa that behind and above the trochlea, and the coronoid fossa.