A cover and support plate arrangement for a wall mounted device, such as a wall switch, display, dimmer, etc., for mounting to a wall box embedded in the wall and having overall surface dimensions greater than that of the wall box. The cover plate is juxtaposed over the front surface of the support plate and is spaced therefrom to provide an air gap between the cover plate and the support plate creating a chimney through which air currents may flow. The device includes an electric circuit having a heat generating device, such as a triac, which is thermally connected to the support plate and in series electrically with a controlled load. The cover plate casts a shadow along vertical sides of the support plate such that the vertical sides of the support plate are visible only when viewed at extreme angles with respect to an imaginary line perpendicular to the plane of the support plate or the wall in which the device is mounted. The cover plate appears to float from the wall while proper thermal dissipation is achieved through the chimney between the cover and support plate. Means are disclosed for constructing a low profile, conventionally sized family of wall mounted dimmer switches that meet Underwriters Laboratories operating temperature standards.