Zigzag plotter
From Tardis Wiki, the free Doctor Who reference
The zigzag plotter was a component in the Doctor's TARDIS which looked like a car gear lever. The zigzag plotter only worked if the operator stood in a specific place while using it. As to WHY remains a mystery. The Eleventh Doctor talked Amy Pond through its use to stop the TARDIS from being thrown into the Time Vortex with only her inside. (DW: The Lodger)
