A longitudinal areal metal element has a surface which extends, perpendicular to the longitudinal direction, from a first outside edge 8 to a second outside edge 9 lying opposite the first outside edge, with the region of the metal element adjoining the first outside edge forming a first side region 14 and the region of the metal element adjoining the second outer edge forming a second side region 15. The side regions are connected to one another by a central region lying between them, and with a plurality of completely bordered apertures 22 being consecutively arranged in the longitudinal direction of the metal element and being formed in the side regions, with its border in each case being formed in one part by said side region and in the other part by the central region. The central region includes a plurality of sections which each consist of two outwardly disposed part sections 31, 33 and a central part section 32 lying between them, with the outwardly disposed part sections being folded over with respect to the central part section for the production of the aperture; with the sections forming part of the borders of the apertures; and with the central region, including the sections, being made in one piece with the two side regions of the metal element. A plurality of folding edges 16, 17 18, 19 are provided which are formed by the folding over of the outwardly disposed sections 31, 33, with respect to the central part section 32 and of which the folding edges 17, 19 disposed more closely to the first outer edge 8 of the metal element point in the direction of the first outer edge and the folding edges 16, 18 disposed more closely to the second outer edge 9 of the metal element point in the opposite way thereto in the direction of the second outer edge.
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