PURPOSE: To move a latch from a set position to a reset position and disengage it from hooks and to improve the operability by horizontally moving a knob of a latch mechanism which holds a press plate overlaid on a base.

CONSTITUTION: In use, a pair of hooks 16 provided on a press plate 3 are fitted to a through hole 40 of an electrical equipment housing case 21 and engaged with the engaging part 63 of a latch 61 of a latch mechanism 31. In order to open the press plate 3 under this state, the operating knob 81 of the latch mechanism 31 is first pressed leftward by a thumb, a latch operating member 71 is rotated counterclockwise about a pivot 72 interlocking with the movement and the cam part 64 of the latch 61 is depressed by the engaging shaft part 73 of the operating member 71. Thus, the latch 61 is rotated counterclockwise about a pivot 62 against a coil spring 66 and moved to a reset position and the engaging part 63 of the latch 61 is disengaged from the hooks 16. Then, by releasing the operating knob 81, the latch 61 is returned to an original position.