There are two little screws with lock washers on the side perpendicular to the two sides the adjustment knobs are on. Loosen them and the knobs will turn no problem. Re-tighten them when finished. One word of advice... don't over-tighten those two screws and be careful loosening them. They are cheap metal (aluminum?) screws that will easily have the head snap off. One of mine did, fortunately in the "tight" position. If I ever have to get it out, I'll need an easy-out.