At the distal end: the carpels in the hand at the head of the ulna and the radius at the ulna notch of radius. At the proximal end: the trochlea of the humerus at the trochlear notch and coronoid process of the ulna and the head of the radius at the radial notch of the ulna.

The radial head articulates with the ulna in the radial notch, and is held in place by the annular ligament.

The ulna has the head at the distal end. Usually the head of a bone is located at the proximal end. The ulna has a large process called the olecranon process that people call their 'elbow'.

olecranon process

Styloid process
Styloid Process