. "FIG. 8A is an explanatory drawing of a connecting portion 46B. FIG. 8B is an explanatory drawing of a connecting portion 46C. FIG. 8C is an explanatory drawing of a connecting portion 46D. FIG. 8D is an explanatory drawing of a connecting portion 46E. FIG. 8E is an explanatory drawing of a connecting portion 46F. Each of the corners 41 a has a right angle in the foregoing embodiment." . . .