This knocker rests on the office door of all past and present Hogwarts Headmasters. It is made of brass and is in the shape of a Griffin. It would have been used a great deal of times since its creation, due to the fact that most visitors will have used it as a precursor to entering the Headmaster's/Headmistress's office. It is known that Harry Potter once avoided its use (involuntarily) by standing outside Professor Dumbledore's office, listening to a conversation between Dumbledore, Cornelius Fudge and Bartemius Crouch Jr. (acting as Alastor Moody at the time), when Bartemius noticed Harry's presence with Alastor Moody's Magical Eye, thus opening the door for Harry.