If you break your key off in a lock, it can be almost impossible to get that key piece out without doing serious damage to your car.
In this instance, an emergency locksmith lock rekeying service would be able to come out and repair your lock without damaging your vehicle.
The locksmith would simply remove the inner workings of the existing lock that contain the snapped off key piece, and then put a new locking mechanism in the lock housing. You are able to go about your business without any damage to the exterior of your car.
This can be especially helpful on those days when it is freezing cold, your lock freezes and the key snaps off.
A professional locksmith can let you know if lock rekeying is the right solution for your situation. You should never work on your auto or home locks on your own. There is a great deal of precision work that goes into door locks that you should leave to a professional.