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A pair of sai.

Sai are tapered metal bars with thumb-like cross guards, which resemble small tridents. Saijustu, the art of using the sai a self-defense tool, is one of the hallmarks of kobudō.

Sai are wielded in pairs because the most prevalent weapons in that era (i.e., the katana and various polearms) were two-handed weapons, which are vulnerable to Kūsankū movements. In general, one sai is used to block, parry, or trap an opponent’s weapon, while the other sai counterattacks. Sai were especially effective against the katana. The katana’s famously sharp edge required construction from extremely hard high-carbon steels, which are brittle. By trapping a blade in its tines and twisting, the sai can apply enough torque to snap a sword in half.

It was once common to carry three sai, and use one as a throwing weapon. Because of their size, weight, and balance, thrown sai are only useful as an atemi directed at an opponent’s feet or legs from ranges less than 20’ (6 m). As such, we do not recommend throwing the sai.


We will not make an in-depth or rigorous study of saijutsu; we will only explain how the sai is used within Goshin-Jutsu. Our weapons serves as a supplement and teaching aid to our empty-hands training, and primarily consists of practicing the and analyzing the bunkai for the following kata:

For more information on saijutsu, please consult Fumio Demura's Karate Weapons of Self-Defense: The Complete Edition, or a used copy of his earlier book, Sai: Karate Weapon of Self-Defense. (Though this might seem like a cop-out, no one can do a decent job of teaching saijutsu without blatantly plagiarizing that book in some way.)


Sai appear flashy and exotic-looking, leading to their frequent appearance in movies, television, and comics -- and with this comes a host of misconceptions, that we want to dispel.

  • “Sais” is not a word. Since the Japanese language has no plural tense, the plural of “sai” is “sai,” just like “sheep” in English.
  • Sai are not bladed. Sai are not knives or cutting tools; they are clubs. Sai tips are tapered so they can be used as a stabbing instrument, but stabbing instruments do not need to be especially sharp or pointy if they have enough force behind them, like driving nails into a board.
  • Sai are not held with the shaft between the middle and index fingers. You cannot use the tines for trapping or use the shaft for striking from this position. This “Ninja Turtle” grip eliminates all of the sai’s advantages. The sai are to be held in one of two ways:
    • The extended grip is like holding a screwdriver. The handle rests diagonally inside of your hand, as high as possible. The fingers wrap around the handle, below the tines. The thumb rests atop the sai’s center-of-mass. The shaft is used for blocking, parrying, striking and thrusting. The tines protect the hand, and are used for trapping and locking weapons for superior parrying.
    • The retracted grip hooks one tine on the web between your thumb and index finger. The index finger runs along the handle, pushing the shaft against the forearm. The shaft fortifies the forearm to stop weapon attacks with regular empty-hand blocks. The handle is used as a striking tool; it’s reduced striking area and rugged construction allows for more powerful punches without hurting your hands. The extra tine can rake an opponent’s eyes or be used to off-balance opponents by hooking their clothing or collarbone.
  • The sai were solely intended to be weapons. The sai are also a part of the martial arts of Malaysia, Indonesia, China, Thailand, and India. Okinawa was centrally-located and in traded with all of these cultures. Sai would have been an easily produced trade good due to their simple construction (a bent bar forge welded to a tapered bar). Sai are small enough to be easily concealed or hidden, which would enable them to remain undetected after the weapons ban. Weapons bans have historically been wildly unpopular, and were (and are) frequently violated. The Japanese and Okinawans have been married to the idea of kobudō as a purely original creation, to the point of creating absurd alternate explanations for why sai exist. These false notions were miscommunicated by well-meaning teachers, who just parroted what their instructors told them. We, who live in the Age of Information, have a duty to put myths to rest. Therefore, please ignore the debunked theories that claim that sai were derived from:
    • Planting tools. While many claim that sai are planting tools, no one has ever given a coherent explanation on how sai are used to plant seeds.
    • Pitchforks. The Okinawans didn’t produce hay, because Asian farming methods are unlike European techniques.
    • Hairpins. While it was common for ladies of that era to use their hairpins as improvised weapons, sai are impractically heavy to be used as hairpins.
      [Photo of a visibly-uncomfortable girl using sai to put her hair in a bun]
    • Hunting Tiger Trident (Chinese Tiger Fork). This traditional polearm is common to many kung-fu styles. The Tiger Fork earned its name when the ancient Chinese empirically determined that it was the best tool for fighting tigers. The kobudō founders had no need for such weapons, since tigers are not indigenous to Okinawa.
    • Nuntebō. The nuntebō is a fisherman’s multi-tool, which combines a spear and a gaff. The nuntebō needed no modifications to be weaponized, and there are kobudō kata for this tool.
    • Jutte. The jutte is a small policeman’s baton from feudal Japan, which features a narrow, thumb-like tine to trap and parry sword blades, or to hook a perpetrator’s clothing. Jutte were not introduced until the beginning of the Edo Period (c.1600 CE), but sai were in use throughout Malaysia, Indonesia, Okinawa, China, Thailand, and India before this. If anything, the jutte was derived from the sai.

Benefits of sai training

Saijustu is admittedly not a practical skill in the modern world. However, there is no way to become good at saijustu without becoming amazing at karate. If you do not utilize the driving power of your legs, maintain perfect stances, or by focusing your techniques (via the unbendable arm, through the tip of the sai), the sai will not work. They will only perform “wet noodle” blocks which will offer no defense, and thus, no opportunity to counter-attack. The sai mandates technique over muscle.

Also, by learning saijutsu, you will gain extreme coordination and dexterity. The sai are a difficult weapon to use. Transitioning from the extended position, to the retracted position, to the extended position again requires great dexterity. These transitions must be performed instantly from a variety of angles, in a smooth and snappy manner. These transitions occur while stepping into a stance, while performing a technique, while trying to stop an armed attacker. This is a daunting task; that is why saijustu is usually reserved for intermediate or advanced students. However, this coordination carries over to your empty-hand fighting. Also, the sai make all other paired weapons seem easy by comparison; by learning saijutsu, you will quickly become proficient with the tonfa, kama, and nitanbō.

Tips on selecting sai

Sai are easily obtained; they are a standard item in martial arts supply stores, websites, and catalogs. The no-frills base-model sai will suit your needs; avoid licensed movie replicas or anything with the “mall ninja” aesthetic. Purchase the size closest to

Measure the length between the tip of your elbow to the tip of your index finger, and purchase the closest sized sai. A retracted sai must cover your entire forearm with its shaft. Some martial artists suggest using sai which are longer than your forearm, to add extra piercing power to rear and outside elbow strikes, but overly-long sai can be awkward to use.