A bō (棒: ぼう) or kon, is a long staff, usually mae of tapered hard wood, for example white oak, bamboo and in some cases for training purposes, rotan. Sometimes it is made of metal or plated with metal for extra strength; also, a full-size bō is sometimes called a rokushakubō (六尺棒: ろくしゃくぼう). This name derives from the Japanese words roku (六: ろく), meaning "six"; shaku (尺: しゃく); a Japanese measurement equivalent to 30.3 centimeters (0.994 foot); and bō. Thus, rokushakubō refers to a staff about 6-shaku (1.82 m; 5.96 feet) long. The bō is typically 3 cm (1.2 inch) thick , sometimes gradually tapering from the middle to 2 cm (0.8 inch)at both ends. This thickness allows the user to make a tight fist around it in order to block and counter an attack. The most common shape, maru-bo, is a round staff, while kaku-bo (four-sided staff), rokkaku-bo (six-sided staff), hakkaku-bo (eight-sided staff) also exist. Other types of bō range from heavy to light, from rigid to highly flexible, and from simply a piece of wood picked up off the side of the road to ornately decorated works of art.