Map Light

That's where the map light is located on the B Bodies. On A Bodies it's and separate metal/plastic housing below the dash usually on the right side. There should also be a small plastic bezel with toggle switch on the driver's side to the left of the steering column to turn it on/off.

Correct

Map light switch (lower left corner of the dash) on my '74 Scamp



On my dad's '73 340 Duster



On my '74 Duster (with Rear Defrosters too. old picture, before I painted the car or installed the interior)



The map light in my '74 Duster is pretty much only good for appearance, since my CD Changer is directly below the map light... oops :D