Cage nut for installation in an elongate, preferably rectangular opening which is only accessible from one side, comprising a nut body with a cylindrical internal thread carrier having an internal thread and an abutment part attached thereto, and a cage encompassing the nut body, wherein the abutment part is adapted to the shape of the opening and has a slightly smaller width and a slightly shorter length than the opening, although the length of the abutment part is significantly greater than the width of the opening; the cage is configured resiliently and is adapted to the shape of the opening such that it can be clipped into the opening and the cage supports stop elements which only allow a rotation of the abutment part with respect to the cage in the screwing-in direction of the internal thread from an installation position parallel to the longitudinal direction of the cage into a retaining position approximately perpendicular thereto.