D-Bubble Fluxer

In the early days of the Type 1 TARDISes, D-Bubble Fluxers were used to imprint the crafts with their interior dimensions. According to the Eleventh Doctor, it was a risky procedure that often did not go as planned.

When he found himself on ancient Gallifrey, he calmed a Type 1 and convinced it to go through the procedure, offering the technicians advice on how to make the process more appealing to the TARDISes. (COMIC: The Lost Dimension)