This sharpening stone, or toishi, is made of dark gray, hard, rectangular carbon stone with metallic flecks. The label attached to the side of the stone reads: "A product by Carbon Stone, Hatahoshico, Ltd." The stone is possibly intended for use to sharpen other stones or to flatten. It serves as an example of the kind of toishi that would have been used in the construction of The Japanese House, though this particular toishi was not used on the project but was brand new when accessioned.