Rounded-off bolts can be a frustrating problem, but there are a few simple tricks that can help you remove them without damaging the bolt or the surrounding material.
One of the most common ways to remove a rounded-off bolt is to use a pair of vice grips. Simply clamp the vice grips onto the bolt and turn it counterclockwise. If the bolt is particularly stubborn, you may need to use a cheater bar or a pair of pliers to get more leverage.