Shoulder

Acromion

How to find it: Follow the scapular spine from medial to lateral until the ridge turns forward. There the bone becomes flat and broad, and that lateral edge is the reference from which shoulder width is measured.
What you use it for: Reference point for the subacromial space: the greater tubercle disappears underneath it during abduction. Also the landmark for the painful arc and for fitting a sling.
On the bone: Scapula
Body region: Shoulder