The adventure of the speckled band
"Did you see something very strange about that bed?" Holmes asked. "It could not be moved, because it was fixed to the floor. Did you ever see a bed like that before?"
"I cannot say that I have."
"The lady could not move her bed. It must always be next to the ventilator and to the rope. We can call it a rope, since it was clearly never meant to be a bell-pull."