I know where the headlight alignment things are... (03 DII disco) but how are you supposed to adjust them while they are all screwed in? Twisting the horizontal and vertical things are easy with the whole headlight assembly out (but impossible to align). How the heck do I do it? What are the measurements for proper alignment?

P.S.... neither headlight is correctly aligned

 

Yes, you must do it while in the trk. You are supposed to park "X" feet from a vertical wall and then they are supposed to center on point "Y". I do not know the specs for a Disco though.
I just adjust mine to what works for me, I do it at night and make my adjustments.

 

I did mine at night. Had the lights facing my neighbors truck and aimed it just below his bumber. it was about 100 feet away. It was hard for me at first. All the alighments were rusted to the plastic, had to use bolt buster and wrenches to twist it. If its hard. take them out, loosen them like i did, them put them back in. should be easier

 

yup!

What I've done in the past is close align them by shining the light on the garage door.

Seems to have worked with me.

 

what did you do... Stick a wrench down the hole? Also... Which nut is for horizontal and which is for vertical, and which way to turn the nut? ( left makes it go up/down left/right?)