To prevent backlash by providing a supporting member to the door of an external case in which circuit breakers or the like are housed, so that when the door is closed and latched, the sliding shaft can be supported for preventing a perpendicular force from being acted on the shaft.

To the shaft 4 of a latch which has been fitted to a door 2, a supporting member 8 for supporting the shaft is fixed. The shape of this supporting member 8 may be arbitrarily selected, and also it can be fixed to the shaft 4. When the door 2 is closed, the inclined surface at the end of the shaft 4 that has been energized by a coil spring is pressed against the hook 3 that has been provided to an external case 1, so that latching is carried out against the force of the spring. In this case, a force perpendicular to the sliding direction (arrow direction) is acted on the shaft 4 that slides in the axial direction, however, this force is supported by the supporting member 8 so that excessive force is prevented from being exerted on the shaft 4, and the engagement of the hook 3 with the shaft 4 is properly maintained. Thus, latching without backlash can be maintained for a long period of time.