Tardis Key

A TARDIS key was the key to the exterior door of a TARDIS. They could be found in a variety of shapes and designs which could be customised by the owners. Whatever the key's shape and size, and whatever form the TARDIS' outer plasmic shell, the key would fit a lock somewhere in the structure.

Use of a TARDIS key enabled entry to a locked TARDIS in the manner of other types of keys, and was not limited by the reconfigurable shape of either the key itself or the outer plasmic shell of the TARDIS. Different TARDIS shells had different locks, whether obvious or hidden, and a TARDIS lock would accept its key even if it was physically larger than the lock. (PROSE: Interference - Book Two)

Because of a metabolism detector behind the lock, (TV: Spearhead from Space) unauthorised people who stole the Doctor's TARDIS key usually found themselves unable to open the TARDIS doors without the Doctor there. (AUDIO: The High Price of Parking, TV: Spearhead from Space) Nevertheless, companions were often able to use the Doctor's key without the Doctor around, (AUDIO: The Jabari Countdown, Lucie Miller) and many had their own keys to the TARDIS. (TV: The Sensorites, Aliens of London, et al.)