a flush - mounted switch , in particular a door - opener switch , for mounting on a fastening surface , has a tubular housing and a flange which protrudes over the cover and an axially moveable button for actuating a switching member connected to the housing . the button is held in its rest position by a restoring force and can be pushed in counter to the action of this restoring force . a fastening ring affixes the door - opener switch on the fastening surface . the flange of the housing covers the fastening ring . a support ring is provided by way of which the button is lockable to the fastening ring .