PURPOSE: To easily obtain a rib lath which is large in strength and is not broken easily by bending and tensile stresses by giving bent shapes to both end parts of each slit in such an extent that they turn inward on the top side, outward on the bottom side and make an acute angle respectively to the lengthwise direction of a sheet.
CONSTITUTION: Since both end parts 18a, 18b of the slit 18 are bent, the bottom part 22 of a side piece 20a branched from a vertical rib 19 is large in width and in strength and, further, since the slit cuts into the vertical rib 19, when the sheet 17 is stretched in a width direction, bending and tensile strengths disperse and no crack is generated in the bottom part 22. Since the bent directions of both end parts 18a, 18b of slit 18 make an acute angle θ to the lengthwise direction (h) of the sheet 17, though the rib lath obtained is bent to the side of a projecting face of the vertical rib 19, the slit cannot be expanded and though the slit is expanded to some extent, the vertical rib 19 is not broken because a distance for short circuit is long.
KATO HIDEO
HOSODA MINORU