To avoid easy removal of a snap ring in mounting a cylinder lock by preventing easy failing with outer force.

A cylinder lock storage portion 4 is formed on the reverse of a mounting member 2 and a groove 6 is formed through a wall 5 of the cylinder lock storage portion 4. In mounting, a snap 7 for formed in a U-shape with a base 8 and a mounting portion 9 extending from both sides of the base is fitted at its outside into the groove 6 and an engagement groove 13 formed in a cylinder lock 11 is engaged with the mounting portion of the snap ring projecting inside the cylinder lock storage portion 4. A stopper 15 is formed on the reverse of the mounting member 2 for restricting the movement of the snap ring 7 to the base 8.