I, too, used the door hanger to get the continental breakfast delivered to my stateroom, on the mornings the ship was at sea.
I put down what juice, cold cereal, toast, and tea, I wanted in the morning, hang it outside on my door, the previous night, and whatever time period I wanted it delivered at, that morning, it was delivered within that time period.
Actually, the room service waiter would call the stateroom before delivering it. I don't know where he was calling from, but, I barely hung up the phone, he was knocking on my stateroom door.
And about a half hour later, he would be knocking on my door again to take away what was left on the breakfast tray.
I never ordered anything else but continental breakfast, but, on my next cruise, I am thinking about getting a suite, just so I can order the full breakfast from room service. Enjoy!