Abstract: A one-piece metal plate has an open mesh-like pattern, a plurality of identical rectangular perforations arranged at regular intervals in parallel rows, a plurality of identical rectangular embossed parts arranged at regular intervals and bridging the rows, and a plurality of identical rectangular web parts. Each of the embossed parts is raised relative to the web parts, and has two opposing overlapping ends extending into the rows. Each of the web parts is confined by two adjacent ones of the perforations and two adjacent ones of the embossed parts. The perforations are aligned along first lines which intersect the rows. The embossed parts are aligned along second lines parallel to the first lines. The first and second lines alternate with one another.