I gave it a try this evening. There are two nuts each side, the outer ones do left to right, the inner ones up and down. There is a diagram on the top of the lamps showing what does what. 8mm nut or you could use a  Philips screwdriver as it is attached to a toothed head  washer. There is a funnel like tube running down to the toothed washer No2 Philips will go down there. Counter clockwise on the nut moves them up, I went up about 12 notches, will need a longer run to see the proper effect, but
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