An improvised weapon is an object that was not designed to be used as a weapon but can be put to that use. They are generally used for self-defence or if the person is otherwise unarmed. In some cases, improvised weapons are commonly used by attackers in street fights, muggings, murders, gang warfare, during riots, or even during insurgencies, usually when conventional weapons such as firearms are unavailable or inappropriate.
Improvised weapons are common everyday objects that can be used in a variety of defensive applications. The objects are not physically altered in any way in an effort to make them more functional as weapons. They are generally used in their normal state.
Other than items designed as weapons, any object that can be used to cause bodily harm can be considered an improvised weapon. Examples of items that have been used as improvised weapons include:
- Sports equipment such as baseball bats, golf clubs, cricket bats, hockey sticks  and dumbbells
- Objects made of glass, such as beer bottles
- Tools such as sledgehammers, tire irons, shovels, fire extinguishers and hammers 
- Construction materials, such as 2×4s, pipes and bricks
- Natural materials, such as rocks
- Garden tools, such as axes, sickles, machetes, pitchforks and pickaxes
- Kitchen utensils, such as kitchen knives, meat mallets and ice picks
- Livestock herding equipment, such as lassos and whips
- Maritime equipment, such as grappling hooks, fishing nets, boat oars, spearguns and docker's hooks
- Recreational toys, such as slingshots and slings
- Furniture, such as chairs
- Vehicles, including rental trucks, light aircraft, such as a Piper PA-28-236 Dakota and airliners, such as the Boeing 767
In martial arts
Throughout history, common tools were used so often as weapons in self-defense that many of them have evolved specifically into weapons or were adapted with the secondary purpose of being used in self-defense, usually by adding modifications to its design. Well-known examples include the Irish shillelagh, the Japanese bō and hanbō, which were originally used as walking canes and the Buddhist Monk's spade, a shovel monks used for burying corpses and often had sharpened edges to defend against bandits with more ease.
Many martial arts use the use of common objects as weapons; Filipino martial arts such as Eskrima include practice with machetes, canes, bamboo spears, and knives as a result of the 333-year Spanish colonization that in the Philippines that prohibited the ownership and use of standard swords and bladed weapons; Chinese martial arts and some Korean martial arts commonly feature the use of improvised weapons such as fans, hammers and staves. There are even some western martial arts that are based on improvised weapons such as British quarterstaff fighting and Irish stick fighting.
Because of the use of common objects as weapons in violent crimes, many countries have laws that prevent the use of some tools and other non-weapon objects to be used for causing harm. It is possible for a person to be detained or even arrested by a law enforcement official or security personnel for carrying a potentially-harmful object if there is no reasonable use for it. For example, it is legal and perfectly understandable for someone to possess a kitchen knife or a hammer and keep it for use in one's home, but it could be judged suspicious for someone to carry a kitchen knife or a hammer concealed on his/her person or in plain sight when walking down a city street.
There are places that prohibit people from entering with objects that may be used as weapons. Most public schools in North America do not allow their students to bring pocket knives, butter knives or chain-wallets, sometimes with harsh zero tolerance policies. Airports typically prohibit objects that could be used as weapons from being carried as a carry-on or in a carry-on bag into the aircraft cabin. The security repercussions after the September 11 attacks saw restrictions widely extended to cover even objects like nail clippers and spiked wristbands.
A makeshift weapon is an everyday object that has been physically altered to enhance its potential as a weapon. It can also be used to refer to common classes of weapons such as guns, knives, and bombs made from commonly available items.
Examples of makeshift weapons include:
- Millwall brick
- Molotov cocktail
- Pipe bomb
- Improvised firearms
- Chainlock (improvised flail)
- Stink bomb
- Smoke bomb
- Improvised explosive device
The improvised Molotov cocktail was used with great success by the heavily outnumbered Finnish forces in the Winter War against the Soviet Union. The mixture of flammable petroleum, often thickened with soap or tar, was so effective against the Soviet tanks that the Finns began mass producing Molotov cocktails, and issuing them to their troops. While the first documented use of such improvised incendiary devices was in the Spanish Civil War, their use in the Winter War was much more prevalent, and it was at that time they were named after the Soviet Foreign Minister Vyacheslav Mikhailovich Molotov.
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