the two white things turn a black toothed-dial. they are used to adjust the normalized hieght of the headlights (meaning that's where the auto level up and down). in my experience, those white knobs are very easy to wear, so be careful, because if you use the wrong tool, you'll scrap out the indent and then you'll have to rotate the black dial which is tougher to turn

and here: forums.e46fanatics.com

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