[Richard]

That is for the taillights to the toad. American was the three wire setup, Foreign was the now standard four wire setup with separate turn signals.

If you look in the stainless panel on the rear side, you will find a box that traces to that switch.

I am a proponent of wiring the toad to have the yellow turn signals flash. I originally wired my toad the old standard way so that the red lights blinked. I had a lot of problems with people seeming ignoring my signals. When I rewired the toad so that the yellows blinked, my sense was that folks payed more attention.