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While Bilbo was sitting and thinking, a thrush flew up with a snail. It was knocking the snail against a rock, and it prodded Bilbo to remember the riddle from the map.
they waited until durins day and a crack appeared
Because it explains to Bilbo why they want to retrieve the treasure stolen by Smaug. Also it proves that there really is a secret door (used by Thorin's father and grandfather.)
They saw a stairway leading to a door.
The Hobbit tells us that the door was green, with a brass knob in the middle.
While Bilbo was sitting and thinking, a thrush flew up with a snail. It was knocking the snail against a rock, and it prodded Bilbo to remember the riddle from the map.
He makes a sign on Bilbo's door that the dwarves interpret to mean "burglar for hire", which brings them into Bilbo's house.
He scratches a secret sign on the door that advertises that an "Expert Burglar" lives here.
none
they waited until durins day and a crack appeared
Because it explains to Bilbo why they want to retrieve the treasure stolen by Smaug. Also it proves that there really is a secret door (used by Thorin's father and grandfather.)
the secret door is in coralines room
The duration of The Secret of the Iron Door is 1.15 hours.
The door turns visible on a specific full moon every so often. The riddle has something to do with the time the thrush cracks the snail. Bilbo hears the thrush crack the snail, and realizes that today is the day the door can be opened.
They saw a stairway leading to a door.
there is no secret door to the snow element yet
The Hobbit tells us that the door was green, with a brass knob in the middle.