A shop in Diagon Alley that sells wizards' robes
I think we’d better do Madam Malkin’s first, Hermione wants new dress robes and Ron’s showing much too much ankle in his school robes, and you must need new ones too, Harry, you’ve grown so much – come on, everyone –
In the back of the shop, a boy with a pale, pointed face was standing on a footstool while a second witch pinned up his long black robes.
Harry Potter and the Philosopher's Stone
There’s something else. We saw Malfoy jump about a mile when Madam Malkin tried to touch his left arm. I think he’s been branded with the Dark Mark.