Pano roof - 4 openings/panels along the exterior for?

My first MB and loving it. 2012 E550
I'm wondering what the 4 small openings/ panels (2 on either side of the exterior roof) are for?
Each one one is a little narrow door that when you open it shows a threaded hole approx 3/8 in.
I'm thinking it's an adjuster for sliding roof alignment?
Pic below - showing flap open and closed.




