Hi Stewart,

A common question. I even saw on a forum once with a knowledgable person pulling someone's leg by saying it was a poisoned shark dart....for emergencies. It's actually a spring-loaded button that releases the lock on the bezel and keeps it from turning accidentally in any direction. I.e., you push and hold the red button, turn the bezel, release the button and the bezel is locked into position.

Cheers

Eyal