To provide a structure which is constituted by inserting an inclined piece of a mounting metallic material into a slit provided on a rear surface side of a decorative plate, passing a through bolt fixed on a bottom plate of the mounting metallic material into a through hole of a bed plate, and screwing a nut in the through bolt on an opposite face of the bed plate and provide the technique of a connection metallic material which is used in this structure.

An inclined slit 25 from a rear surface of a decorative plate 22 to the halfway of the plate thickness is provided, a storage groove 23 is drilled on a surface of a bed plate 21, and a through hole 24 is drilled along the storage groove 23. On the other hand, a connection metal fitting 26 is constituted by a decorative plate mounting metallic material 27 in which inclined pieces 31a, 31b are provided continuously in a bottom plate 30 and a through bolt 28 and a nut 29 which can be fixed on the decorative plate mounting metal fitting 27. Next, the inclined pieces 31a, 31b are inserted into an inclined slit 25 of the decorative plate 22 to arrange the bottom plate 30 in the storage groove 23. The through bolt 28 is inserted into the through hole 24, and the nut 29 is screwed in the through bolt 28 exposed on a rear surface of the bed plate 21 to attach the decorative plate 22 on the bed plate 21.