Front Entrance

When a wizard approaches number twelve, Grimmauld Place who knows of its location, it appears to shove its neighboring houses, number eleven and number thirteen, out of the way as it appears between them. What's revealed is a worn set of front steps, leading to a battered front door. On the door is a silver knocker in the shape of a twisted serpent, with no keyholes, handles, or anything else that would indicate it to be a door, as it opens only by magic. When one leaves the house, the building vanishes behind him the instant he reaches the street.