The Unshu abacus was born in Okuizumo Town, Shimane Prefecture, and is a designated traditional craft in Japan. The first of its kind was reportedly made in Kametaka in about 1830 by a carpenter. The most important component of an abacus is the beads, which should move freely and produce a clear click when they hit the frame or another bead. Craftsmen therefore pay close attention to the finish of the bamboo shafts and bead holes. The abacus frame is made of oak, ebony, or other strong wood, the shafts are made from smoked or processed bamboo, and the beads are usually made from plum, birch, boxwood or ebony wood. All materials are carefully inspected, and only those that are sufficiently dry and free of warping are used. Unshu abacuses continue to improve in quality the longer they are used.