Incidentally, the key is so short because many of these locks were fitted to the outside of the door as 'cut locks', what US readers will know as 'half-mortise'. This method of fitting is mainly used for cabinet locks — and cell locks. Before the availability of motor vehicles, constables had to walk everywhere so Britain had many small local police stations for beat constables. Many such stations had only two cells. With very little popular knowledge of how to defeat locks, simple but sturdy, and cheap, was adequate. Many of the occupants were drunks and petty thieves.