you sure have missed some other threads... hahaha... lock-to-lock is clearly a steering angle resetting procedure, while double lock is the central locking system function, when the car is double locked (available in many german made cars)...when the car is double locked (in US, it means arming the alarm, as alarm is a STANDARD feauture in US-bound cars), the locks, the trunk, the fuel cover are all locked up, and can not be opened from inside with a standard double-tug on the inside handle. I believe the only exception to that is the trunk and possibly the top hatch on the X, due to some Federal regulations in the US. in case of power failure, the driver's door still can be opened mechanically, then power restored and the rest of the doors can be opened...