Zeus plugs, also spelt Zeus Plugs (PROSE: Apocrypha Bipedium) or zeus plugs, (PROSE: Doctor Who and the Hand of Fear) were tools used in the maintenance of TARDISes.
Zeus plugs were inserted into Ganymede sockets. (PROSE: Apocrypha Bipedium)
Quadrigger Stoyn had a Zeus plug in his workcase which he was using to work on the Doctor's TARDIS shortly before the First Doctor stole it. (AUDIO: The Beginning)
The Fourth Doctor decided he didn't need the plugs to repair the predicted damage to his TARDIS's thermocouplings. (TV: The Hand of Fear) He later used a Zeus plug to incapacitate a Movellan. (AUDIO: The Movellan Grave)
The Tenth Doctor needed his Zeus plugs to close the time windows aboard the SS Madame de Pompdour. He was unable to find them but recalled using them moments before as castanets at a French party. (TV: The Girl in the Fireplace)