Abstract: A mounting rail, particularly for use in building construction, is formed by an elongated rail member (2) of approximately C-shaped cross section having a rear wall (3) with spaced openings (7a-7d) therethrough and pair of side walls (4a, 4b) extending from and at substantially right angles to the rear wall (3). The side walls have free edge sections spaced from the rear wall bent inwardly towards one another and forming cross members (5a, 5b) extending generally parallel to the rear wall with the inner edges of the cross members spaced apart and forming a slot (6) extending in the elongated direction of the rail member (2). Each side wall (4a, 4b) has shaped recesses (8a, 8b) extending for the length of the rail member (2). The shaped recesses (8a, 8b) are arranged symmetrically to one another in the opposite sidewalls (4a, 4b) and have a depth of (d) which does not exceed the width (b) of the cross members (5a, 5b) defining the slot (6).