The ends of the manipulator arms typically were shaped like a plunger. For this reason, Dalek technology often had circular controls which the Daleks could arm or disarm by rotating. The black tip at the end, which gave the arm its "plunger" shape, could alter its form to better interact with specific objects, for example, finding the combination of electronically-locked doors. (TV: Dalek) Imperial Daleks had a more conical variant, with a slotted rim specifically designed to operate controls. (TV: Remembrance of the Daleks)