Brass knuckles Brass knuckles , also sometimes called knuckles , knucks , brass knucks , knucklebusters , or knuckledusters , are weapon s used in hand - to - hand combat . Brass knuckles are pieces of metal shaped to fit around the knuckle s . Despite their name , they are usually made of steel . Designed to preserve and concentrate a punch ' s force by directing it toward a harder and smaller contact area , they result in increased tissue disruption , including an increased likelihood of fracturing the victim ' s bones on impact . The extended and rounded palm grip also spreads across the attacker ' s palm the counter - force that would otherwise be absorbed primarily by the attacker ' s fingers , reducing the likelihood of damage to the attacker ' s fingers . History and variations . Metal ring and knuckle style weapons date back to ancient times and have been used all over the world for many hundreds of years . The Nihang Singh s used a early varient called Sher Panja in the 18 century . Cast iron , brass , lead , and wood knuckles were made in the United States during the American Civil War ( 1861 – 1865 ) . Soldiers would often buy cast iron or brass knuckles . If they could not buy them , they would carve their own from wood , or cast them at camp by melting lead bullets and using a mold in the dirt . Some brass knuckles have rounded rings , which increase the impact of blows . Other instruments ( not generally considered to be " brass knuckles " or " metal knuckles " " per se " ) may have spikes , sharp points and cutting edges . These devices come in many variations and are called by a variety of names , including " knuckle knives . " By the late 19th century , knuckledusters were incorporated into various kinds of pistols like the Apache revolver s used by criminals in France in the late 19th century to early 20th century . During World War I the US Army issued two different knuckle knives , the US model 1917 and US model 1918 Mark I trench knives . Knuckles and knuckle knives were also being made in England at the time and purchased privately by British soldiers . By World War II , knuckles and knuckle knives were quite popular with both American and British soldiers . The Model 1918 trench knives were reissued to American paratroopers . British Commandos even had their very own " Death ' s Head " knuckle knife , featuring a skull - shaped brass knuckle handle . A notable knuckle knife still in use is the Cuchillo de Paracaidista , issued to Argentinian paratroopers . Current - issue models have an emergency blade in the crossguard . Legality and distribution . In Canada , brass knuckles , also referred to as " brass monkeys " , or any similar devices , are listed as prohibited weapons ; possession of such weapon is a criminal offence under the Criminal Code of Canada . Similar legislation has been instituted in Russia and Australia . In France , brass knuckles are legal , and freely sold to people of legal age ( over 18 years old ) , but carrying them is forbidden . The French term is " poing américain " , which literally means " American fist " . In Sweden , brass knuckles are legal to purchase and own , but are not legal to sell or carry in public . The carrying of brass knuckles carry the same penalty as carrying a knife , and falls under the same law . They are called " knogjärn " , literally " knuckle iron " . In Brazil , brass knuckles are legal and freely sold . They are called " Soco Inglês , " which means " English Punch . " Brass knuckles are illegal in the United Kingdom , Norway , Portugal , Spain , Austria , Croatia , Germany , Belgium , Bosnia and the Netherlands , carrying significant jail sentences and fines for possession of a dangerous weapon . In the United States , brass knuckles are not significantly regulated at the federal level , but various state , county and city laws prohibit their purchase and / or possession . Some state laws require purchasers to be 18 or older . Most states have statutes regulating the carrying of weapons , and many specifically prohibit brass knuckles or " metal knuckles . " Where they are legal , brass knuckles can normally be purchased online or at flea market s , swap meet s , and at some sword and weapon shops . Some companies manufacture belt buckles or novelty paper weights that function as brass knuckles and are sold " for entertainment purposes only , " a dubious legal standing . Brass knuckles made of hardened plastic , rather than metal , have been marketed as " undetectable by airport metal detectors . " A number of states that ban brass knuckles also ban plastic knuckles . New York ' s criminal law statutes list both " metal knuckles " and " plastic knuckles " as prohibited weapons , but provide no definition for either . Texas does not differentiate with regards to composition materials , making the possession of " knuckles " a Class A misdemeanor . Specifically , Texas makes it an offense to intentionally or knowingly possess , manufacture , transport , repair , or sell prohibited weapons ( including knuckles ) .