The most common tool bike thieves use is a pair of bolt cutters. These can cut through most cable locks and even some U-locks, but other U-Locks and chain locks will require an angle grinder. Angle grinders are quite loud and throw a lot of sparks, so if your lock can withstand bolt cutter attacks, it’s already well ahead in the safety game. For the toughest locks, thieves may use torches or other heavy-duty tools. Less commonly, thieves may use chemicals that will freeze the lock, making it more susceptible to damage.