"Sell them a key that keeps shrinking to nothing so they can never find it when they need it. …Of course, it's very hard to convict anyone because no Muggle would admit their key keeps shrinking — they'll insist they just keep losing it."
Arthur Weasley[src]

A shrinking key is a key that has been enchanted to constantly disappear on its owner after a period of shrinking. Magical pranksters sell these keys to Muggles, who, being unaware of the wizarding world, will simply insist that they are always misplacing them.[1]


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