When replacing a CH switch in a Triumph, you are required to enlarge the aperture by removing the thin metal plate the old switch clipped into. The new switch will then fit, but will have no positive engagement as the fins on the body will not reach the back of the dashboard.

The original clip was supplied by Lucas / Triumph when dealers where replacing the CH parts. It slips over the back of the switch when it is inserted into the dashboard, and then clips into the two recesses found on the Lucas replacement switches. The rest of the clip is then 'pushing' against the back of the dashboard, and effectively pulls the switch into place on the dashboard front.