Originally Posted by KerryIrons

Let's be clear about this. When Kontact said to rotate the brake, he meant that the brake body must actually move relative to the frame. Lots of people just push on one of the brake arms and think that they are centering the brake. That's not how it works and after a few applications of the brakes, they will be off-center again. If you can't move the brake body by hand, then loosen the attachment bolt, center the brake, and tighten the attachment bolt while making sure that the brake body doesn't move. You might need to do this a couple of times to get it right. I always tighten my brake attachment bolts such that the brakes can't easily be knocked off center, but so that I can move the brake body with significant hand force.