A construction unit (1, 2) forms part of a gas heater and includes a valve (9) which is actuatable by way of a stem (10). The stem (10) includes positive-fit device. The stem (10) is controllable from the outside via a tool which can be brought into engagement with the positive fit device. A detent engagement device (18, 27) holds the tool (21) in engagement with the stem (10), so that the valve is controllable without the aid of outside tools.

The present application relates to apparatus for mounting on a rotatable portion of a diesel filter for controlling a drainage valve. The apparatus comprises an outlet for draining liquid from the diesel filter, mounting apparatus for fixedly mounting the apparatus on the rotatable portion, and a manipulation portion for manipulation by a user's hand which projects, at least in part, radially outward from said rotatable portion, in use. The application also relates to a finger grip wheel for a diesel filter. The finger grip wheel has a drainage outlet and at least one finger detent for accommodating a tip of a user's finger to facilitate rotation of the finger grip wheel.

A handle assembly and related methods for actuating a mechanism such as a disconnect switch.