A housing contains a device such as an electrical switch and a handle is mounted on a cover of the housing. The handle is rotatable between first and second positions. The handle is coupled to the device within the housing so that when the handle rotates, the device is changed from one state to another. An annular wall partially surrounds the handle, the wall having end faces which limit the rotational movement of the handle. The wall and the handle have holes which can be aligned in one position of the handle and held in that position by inserting the shackle of a lock. With this structure, a switch can be locked in an off or on position to inhibit unauthorized changing of the switch position.