2003 GMC Yukon Owner's Manual - Page 358

Power Winches If you wish to use a power winch on your vehicle, only use it when your vehicle is stationary or anchored. Step-Bumper Pad Your vehicle has a rear step bumper with a rear step pad at the center of the bumper. If you will be using the bumper to tow a trailer, and your step-bumper has three cutout circles you must push out the center cutout circle to install the trailer ball. If your step-bumper has only one cutout circle, you will have to cut out the circle, then remove it to install the trailer ball. 4-76