Docking clamp
From Tardis Wiki, the free Doctor Who reference
A docking clamp connected the dome of a Dalek to their upper grating section. By releasing their docking clamp, a Dalek could open up their dome, exposing their mutant form. (TV: Resurrection of the Daleks)
While operating a vacant Dalek casing within the Moroks' Space Museum, the First Doctor opened up the dome to peek his head out of the casing. (TV: The Space Museum)
