The Jo is made of hardwood and averages about 50 inches in length and 7/8 off an inch in diameter. It is round or octagonal in cross section. These dimensions are not critical to the techniques, but for practice with a partner, a staff of standard length is desirable and for practice alone, staff long enough to pass just underneath your armpit when standing is adequate.

The Jo is sometimes called the four-foot staff or short staff to distinguish it from the long staff or rokushaku bo (six-foot stick), and the half stick or hambo (three-foot stick).

The history of the Jo includes a divine birth and a noble heritage. It begins in the early 1600s, when a samurai named Muso Gonnosuke meditated in the mountains after his first and only defeat., at the hands of Japan's greatest swordsman, Miyamoto Musachi. Muso's favourite weapon was the bo - the long or six-foot staff. Miyamoto, using both a long and a short sword, had blocked the staff in such a way that Muso could not withdraw his weapon safely. Miyamoto spared Muso's life, however, and left him to meditate on his defeat.

The result of Muso's meditation was a "divine insight" that led him to develop a shorter staff and a style of fighting with it. He called his style shindo muso ryu jojutso, and with it, he defeated Miyamoto in a second dual. He, too, spared his opponent's life and became the only man ever to best the master swordsman.

Because it was developed to use against swordsman, jojutsu is heavily influenced by sword techniques, particularly in striking, fencing postures and receiving actions. The Jo is also a pole arm, however and incorporates the thrusts, sweeps, entering motions, and receiving actions of the spear (yari) and halberd (naginata).

The Jo was adapted by Uyeshiba Morihei, the founder of Aikido, to teach the principles of Aikido. His use of the weapon is called aikijo. Aikijo resembles jodo in that both involve fencing. Jodo techniques are often faster and sharper because angular attacks and defences are part of it combat orientation. Aikijo techniques are slower and softer because circular movements can blend attacks and defences and reduce the attitude of conflict.

The Jo, then, is a humble weapon with a noble history; a simple weapon capable of great complexity.