A kotoji is a bridge of koto or sō (Chinese harp) used to support the strings and change pitch. These pieces seem to have been used for twelve-string shiragi-goto (koto for music of Shiragi), judging from their shapes. Looking form the front, each of them appears like a flat-top mountain, with curved sides spreading out towards a wide base. There are ditches for the strings on top, while the underside has an inverted curve between the base supports. The surface was first dyed with purplish-red su plant pigment (suou) and then lacquered. This technique is called sekishitsu (red-lacquer). The front and backside are decorated with a leaf-pattern in kirihaku (cut-foil), with kirikane (metal-strips) applied on the upper part. As these kotoji are made of three different materials, it is thought that they were attached to different koto.