A rotor saved is a rotor earned.
Disc Brakes have been a great advancement for mountain bikes. We love them and can barely remember bikes with anything but. However, sometimes demanding terrain, heat buildup, or even packing and shipping a bike will leave a rotor out of true. They may get bent easily, especially the larger 180-200mm discs, but as easily as they bend the wrong way, you can bend them right back into shape with the Park Tool DT-2 Rotor Truing Fork. Truing disc rotors is actually much easier than truing wheels, so there is no excuse to hear them dragging as you ride down the trail.
The Park Tool DT-2 Rotor Truing Fork is laser cut from tool steel and features two narrow slots, just big enough to slide over the thickness of the brake rotor -- one at 90° that works really well for manipulating the spokes on the rotor and another at a shallower angle that allows you to gently work the braking surface of the disc without scraping your knuckles against the spokes.