Key to the Side-door

The Key to the Side-door was a small, curious-looking silver key with a long barrel, cut for the hidden keyhole of the secret entrance into the Lonely Mountain. Thrór and his son Thráin had it made along with the map, at some time before the mountain fell, and the two were always kept together. Thráin gave the key to Gandalf in the year 2850 of the Third Age, in the dungeons of the Necromancer, shortly before he died there. Gandalf handed key and map to Thorin on the day he and his fellow Dwarves called on Bilbo at Bag End in late April of 2941, and from that moment Thorin kept it fastened to a chain about his neck.