Good afternoon!

Putting in a new brake light switch on my 1950 3800, the type that sits on the outside of the firewall with the little arm that gets released when you press down on the pedal. The switch has 2 wire terminals - one in the middle, one on the right as you look at it installed. Which of the terminals takes power from the fusebox? Any ideas? The terminals don't have any markings on them.

Thanks - Bruce