Figure 9. Pearl shell hand graters (tuai), 4 to 7 inches long, 0.5 to 0.75 inches wide at hinge end, and 1.25 to 1.75 at other end. a, front and side views of short implement made without hinge of shell, back ground to remove roughness, 0.1 to 0.15 inches thick: 1, upper hinge end, narrow with rounded point; 2, lower grating, convex from side to side and not serrated. b, front and side views of longer implement, thick hinge part of upper end and lower edge ground from back: 1, upper end, part of hinge included; 2, lower end, serrated cutting edge.