Butterfly sword The butterfly sword ( ) is a short dāo , or single - edged blade , originally from the South of China , though it has seen use in the North . The blade of a butterfly sword is roughly as long as a human forearm , which allows for easy concealment inside loose sleeves or boots , and allows greater maneuverability when spinning and rotating during close - quarters fighting . Butterfly swords are usually wielded in pairs . A pair of swords will often be carried side by side within the same scabbard , so as to give the appearance of a single weapon . The butterfly sword has a small crossguard to protect the hands of the wielder , similar to that of a " sai " , which can also be used to block or hook an opponent ' s weapon . In some versions the crossguard is enlarged offering a second handhold , held in this position the swords can be manipulated in a manner akin to a pair of tonfa . They may also be used as brass knuckles when non - lethal application of the weapon is desired . Traditionally , the blade of a butterfly sword is only sharpened along half of its edge - from the middle of the blade to the tip ; this can be seen in all vintage specimens from the Qing Dynasty . The blade from the midpoint down is left blunt so that it can be used to deliver non - lethal strikes and to block without damaging the sharpened edge . Butterflies were generally commissioned for individual martial artists , not mass produced , so every set of swords is different , however an average blade today is about 11½ " long with a 6 " handle . Other terms . Butterfly swords are usually called ' butterfly knives ' in English . However , they should not be confused with the folding balisong , which is also commonly called a butterfly knife . The Chinese word dāo is used to designate any blade whose primary function is to cut and slash regardless of length . In some branches of Kung Fu , such as Wing Chun , butterfly knives are known as Baat Jaam Do ( named after the Systems form , literally ' Eight Chopping / Slashing Knives ' in Cantonese ) . Usage . Butterfly swords are used in several Chinese martial arts , notably Wing Chun , Shaolin , Lau Gar , Hung Gar and Choy Lay Fut . In Wing Chun , one notable aspect of butterfly sword combat is that its principles are the basis for all other weaponry . In theory , any object that can be held in the hands of a Wing Chun practitioner will follow the same basic principles of movement as the butterfly swords . This is because the use of butterfly swords is simply an extension of empty - handed combat . The design of the weapon , including the quillon ( crossguard ) shape , blade profile and blade length , are specific to each style of martial arts , the precise lineage , and individual . For example , some martial arts lineages flip the butterfly swords between the forward and reverse grip like a Sai , and consequently need a quillon that will fit the hand during a reverse grip . Some lineages trap the opponent ' s staff or blade between the quillon and spine , and they need a longer quillon closer and more parallel to the spine than would fit a hand after flipping . Some schools like a hybrid quillon design that is adequate for both flipping and trapping , but optimal for neither . Chinese War Era butterfly swords had a long narrow blade that emphasized stabbing . While a deadly stabbing blade with a sharpened swage — known as " Red Boat " knives — was used by Chinese revolutionaries in the Wing Chun lineage , modern Wing Chun practitioners tend to prefer a blade profile with a wider belly that emphasizes chopping and slashing . Wing Chun lore attributes this to the desire of Monks to maim rather than kill . These knives generally have a quarter circle style tip suitable only for chopping / slashing and not stabbing , or a shallower curve to a more pointy tip that will accommodate both . The appropriate length of the blade is a combination of the lineage and individual . For a Hung Gar stylist , the length should be a few inches past the elbow when the knife is held in a reverse grip . Wing Chun schools that use techniques which twirl the knives inside the arm need a reverse grip blade length based on the distance to the interior of the bicep . Other Wing Chun schools measure to the outside of the bicep . Butterfly swords are regarded by many Chinese martial artists to hold the most versatility and balance of offensive and defensive capabilities of any Chinese weapon , with many more capabilities than just a weapon .