A bell pull remains in situ to the north of the door.
The family summons him with an ever-present bell pull (in the form of a hangman's noose).
Bell pulls are used to summon workers in homes of people who have butlers, maids or other servants, and often have a tassel at the bottom.
Holmes was able to see that the picture was kept in a recess behind a sliding panel just above the right bell pull.
Then he discovered a rusty bell pull and gave it a sharp tug.
He waited to hear no more, but went forward where there were bell pulls on the deck, and rang two bells to stop her.
