I always thought the "master key" is the gasoline abrasive saw I always see FDNY use - man, those guys cut anything with them - watching them take down roll-up steel grates is fun - or take down a section of iron fence. Saw a kid get impaled on the points of one of those steel fences outside a school - they took down a good sized section of the fence and loaded the kid in the ambulance with about a 3ftx3ft section of fence still attached - according to the news, the kid not only lived, but made a full recovery