Lockers on a Jeep are a type of differential that "locks" both wheels of the same axle together so they both move at the same speed. Most stock Jeeps come with an open differential, which works well until one wheel gets stuck and only that wheel spins. Lockers are useful for off-roading and difficult trails, as they help the Jeep get through more difficult terrain and give the driver a first option for self-recovery if the Jeep gets stuck. Lockers can be a leading cause of differential failure and broken axles, so its important to understand how they function and when to use them. In extreme terrain like rock crawling, lockers may only be on for a few yards of the trail at a time, switched off and on again as the driver works through obstacles. If a Jeep does not come with locking differentials standard, then the driver can purchase aftermarket differentials and have them installed.