In Harry Potter and the Deathly Hallows, Dumbledore engraved a cryptic message on the Golden Snitch that Harry swallowed in his first quidditch match: I open at the close. It took Harry many grueling days to figure that one out, until the time came, on the Final Battle at Hogwarts, that he let all his guards down, eventually unveiling the answer to the message: I open at the close.