There are a few things you can do before attempting the knob adjustment. If you are shooting (poi) left, there is a pad w/ 2 protrusions at the back of the mount, not the base, those need to be filed down ever so slightly. A stone would be better. If you are shooting right, you need a shim. W/ the windage adjustment, you loosen the screws, pull up on the knob and bring the disk to zero. Depress the knob and tighten. This is fine for minor adjustment as it will move the reticule.