Originally Posted by
lungimsam
As far as I know, you should be able to see movement so that you can line up the pulley with the inner or outer cog, whichever limit you are adjusting for.
I could see the rear derailer pulley moving with every turn of the "H" screw that worked, so that I could line it up easily with the cog. I can turn the other three (the "L" on the rear derailer, and the "h" and "L" on the front derailer) in any direction down or back, with no movement.
In that instance, you saw movement because the 'H' screw was touching the tab on the RD and forcing it inward. If the screw is not contacting the tab when you turn it, or you are turning counter-clockwise to allow more movement, it won't move the derailleur because the screw is going away from the tab. I'm not a fan of having contact and forcing the derailleur to move. I prefer to turn the limit screw while not in contact, test the shifting, and repeat until it's good.