PURPOSE: To obtain the joining of good appearance with simple finish without any possibility for warpage by welding a pair of plate metals to be contact-projectively joined to each other by means of the straps having the conveyxly projecting parts to be interposed in their contact-projecting faces and the abutment parts to be abutted on one surface of the plate metals.

CONSTITUTION: A frame body decorating the opening edge of the body of lighting fixture consists of a frame 1 and kick springs 2 detaining this to the body. This frame 1 is formed by joining four metal plates 1aW1d at the corner parts. At this time, the projecting parts 6 and joining parts 7 of straps 5 formed into a T shape by the same material are interposed between the faying surfaces of the plate metls 1a, 1b respectively so as to be abutted on their one surface, thence they are spot-welded by a welding tip 8, and the ends of the projecting parts 6 are ground. Since this grinding is only for the end of the projecting parts 6, it is extremely simple. Since the intervention of the projecting parts 6 lets the faying surfaces to be welded as well, no seams appear when finishing by grinding is performed. In addition, the spot welding is made by the straps 5 and therefore there is no fear for the occurrence of warpage.