A door lock and key set is an essential part of a cars security system. In conjunction with several other components the door locks and keys allow the doors to be locked and unlocked via a key from outside the vehicle.

<Model> door lock and key sets generally include 3 units, one for each of the front doors and one for the bootlid or tailgate. The lock barrel is installed behind the door card or lining panel, and presents a keyhole to the outside of the door. The door lock barrel is connected to the door lock mechanism allowing it to be locked and unlocked. In cars with central locking systems the door lock barrel is also connected electronically to the ECU, allowing all doors to be locked and unlocked from one location. Additionally the ECU may be used to activate and deactivate alarm and immobiliser systems when the key is turned in the lock barrel.

Door lock barrels can fail due to wear and tear including damaged or worn keys, corrosion, damaged wiring (where connected to central locking) or due to attempted theft. The major advantage to installing a door locks and keys complete set is that all locks will use the same key.