Abstract: For producing a device for controlling the flow of a medium, having a housing and a flap supported pivotably in it between a closing position and an open position, which flap in its closing position rests with its peripheral region on stop faces of the housing that are present on both sides of the longitudinal axis, to create tightness in the closing position in later operation, the flap is subjected to a force which is selected, taking into account the material comprising the stop faces and the flap, such that the flap with its peripheral region rests on at least one stop face at least substantially with linear contact. The force can be selected such that the housing, in the region of at least one stop face, and/or the flap, in its peripheral region, is permanently deformed. The housing and the flap are of metal.