To regulate the increasing lengths of shinai, the Kobusho (a military academy set up by the Edo Shogunate) declared in 1856 that, 'shinai longer than 3 jaku 8 sun (about 95cm) are not acceptable' and this became the set length.
その長大化に歯止めをかけるべく、安政3年に講武所では「撓は柄共総長サ尺貫法ニて三尺八寸より長きは不相成」と3尺8寸までと決めた。