A locking device for locking a displaceable motor vehicle part which is lockable by the means of the locking device within a displacement range in a respective rest position reached by displacement is provided. The locking device comprising a braking device with at least two braking elements which interacts in a braking manner in a respective rest position of the motor vehicle part in order to lock the motor vehicle part, and which can be brought into a position without braking engagement by inducing a release force into the braking device. An actuator is assigned to the locking device, which is optionally combinable with the braking device and with which a displacement movement of the motor vehicle part is brakable for locking the motor vehicle part.