Dumbwaiter Directions is a written note found in The Knife of Dunwall.
Place the items you wish to deliver on the tray. Use the dial to select the floor, with (1) as the law offices and lobby, (2) as the smoking lounge and library, (3) Timsh's office, and (4) as the dining hall and bedroom. Pull the lever and the platform will go up. When it reaches that floor a bell will sound to notify the staff on that floor. Once the load has been removed from the platform, the machine will automatically lower it back down. If you activate the dumbwaiter without selecting a floor, it will default to (1).