PURPOSE: To prevent a shackle from being cut off by bringing wall sections covering both sides of the shackle near to the shackle, and integrally forming the wall sections from the upper ends of both sides of a main body section.

CONSTITUTION: In a cylinder lock 1, an inverted U-shaped shackle 3 is projected upwards from a main body section 2, and wall sections 5 and 6 covering both ends of the shackle 3 are formed integrally from the upper ends of both sides of the main body section 2 so as to be brought near to the shackle 3. The height of these wall sections 5 and 6 is formed in approximately the same height as the upper end of the shackle 3 under a locked state. The shackle 3 of such a cylinder lock 1 is engaged with annular fittings 9 under the state, in which a door 8 is closed and the annular fittings 9 are inserted into the hole 7a of fittings 7 with the hole. The wall sections 5 and 6 are formed so as to be brought near to the shackle 3 and the annular fittings 9 cannot be moved at the places of the wall sections 5 and 6 at that time, and the shackle 3 is difficult to be gripped by the front end of a wire clipper, etc., thus the shackle 3 is hard to cut.