Sirius Black's penknife

The enchanted knife was given to Harry Potter by Sirius Black for Christmas. It was said to open all doors whether mechanically or magicaly sealed. To use it, it has to slide down the side of the door and then it would open.

In the Department of Mysteries Harry tried to use it to open a door to the Love room but it melted and was never mended.

Appearances

 * Harry Potter and the Goblet of Fire
 * Harry Potter and the Order of the Phoenix