Abstract: A reversible fixture mount for use with siding for a building structure and comprising a pair of mating members, each member including a base having front and rear faces, side walls extending from the base and a flange extending outwardly from the margin of the side walls opposite the base. Each member is a mirror image of the other except for a groove on one member which engages a support on the other to define a lap joint. The support extends from the rear face of the base to a plane defined by the flanges to provide support for the central portion of the base when the flange has engaged the building structure, the front faces of the members defining a second plane parallel to the plane defined by the flanges and the support.