Just curious. On the exterior of the headlight lens'. There are some protrusions that look like littles nipples. Does anyone know what they're for?

 

Inspection stations as some mechanics have these levels that mount on the surface of the headlamps. These mounts attach to the three nipples on the lens. A lot of cars theseadays don't have the nipples because manufacturers are including level sights on the headlamp assemblies.