To provide a cylindrical lock acting in a mechanism different from a convenional mechanism, by targeting at a safe, secure and high security lock.

Eight projections exist on an inner surface of a lock outer cylinder 8, and a point 23 of two stoppers 22 also exists. When these positions are not adjusted to two kinds of an outside surface of a key 11, that is, vertical lines 15 and 18 of four pieces of a projection system and two pieces of a stopper system, the key 11 cannot be inserted, and when the positions do not coincide with horizontal lines 16 and 19 of two pieces of the projection system and one piece of the stopper system, the key 11 cannot be rotated. This lock is formed as a structure unable to rotate the key 11 when a position and the depth of a regulating hole 25 of a rotary board 13 are not adjusted to a pin 30 of the key 11. The lock is formed as a structure unable to operate opening-closing of the lock if one of these conditions lacks.

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