Rotating bolt is a method of locking

Lock (firearm)

The lock of a firearm is the system used to ignite the propellant. Types of lock include snaplock, matchlock, wheellock, flintlock, modern percussion, rotating bolt, and experimental electronic types. A complete firearm often consists of lock, stock, and barrel...

 originally developed by Ferdinand Ritter von Mannlicher and found in his Steyr-Mannlicher M1895

Steyr-Mannlicher M1895

The Steyr-Mannlicher M1895 rifle is a bolt-action rifle, designed by Ferdinand Ritter von Mannlicher that used a refined version of his revolutionary straight-pull action. It was nicknamed the "Ruck-Zuck" by Landsers...

 straight-pull bolt-action rifle designed for and issued to the Austro-Hungarian Army. It was later evolved for use in gas operated, semi-automatic

Semi-automatic firearm

A semi-automatic, or self-loading firearm is a weapon which performs all steps necessary to prepare the weapon to fire again after firing—assuming cartridges remain in the weapon's feed device or magazine...

 or selective fire

Selective fire

A selective fire firearm has at least one semi–automatic and one automatic mode, which is activated by means of a selector which varies depending on the weapon's design. Some selective fire weapons utilize burst fire mechanisms to limit the maximum or total number of shots fired automatically in...

 firearms (such as the M1

M1 Garand

The M1 Garand , was the first semi-automatic rifle to be generally issued to the infantry of any nation. Called "the greatest battle implement ever devised" by General George S...

, M14

M14 rifle

The M14 rifle, formally the United States Rifle, 7.62 mm, M14, is an American selective fire automatic rifle firing 7.62x51mm NATO  ammunition. It was the standard issue U.S. rifle from 1959 to 1970. The M14 was used for U.S...

, M16

M16 rifle

The M16 is the United States military designation for the AR-15 rifle adapted for both semi-automatic and full-automatic fire. Colt purchased the rights to the AR-15 from ArmaLite, and currently uses that designation only for semi-automatic versions of the rifle. The M16 fires the 5.56×45mm NATO...

, the L85A1/A2 and the AK-47

AK-47

The AK-47 is a selective-fire, gas-operated 7.62×39mm assault rifle, first developed in the Soviet Union by Mikhail Kalashnikov. It is officially known as Avtomat Kalashnikova . It is also known as a Kalashnikov, an "AK", or in Russian slang, Kalash.Design work on the AK-47 began in the last year...

/74

AK-74

The AK-74 is an assault rifle developed in the early 1970s in the Soviet Union as the replacement for the earlier AKM...

) in which the bolt

Bolt (firearm)

A bolt is a mechanical part of a firearm that blocks the rear of the chamber while the propellant burns.In manually-operated firearms, such as bolt-action, lever-action, and pump-action rifles and shotguns, the bolt is held fixed by its locking lugs during firing, forcing all the expanding gas...

, upon contact with the breech

Breech-loading weapon

A breech-loading weapon is a firearm in which the cartridge or shell is inserted or loaded into a chamber integral to the rear portion of a barrel....

, rotates and locks into place, being held in place by lugs attached to the breech or barrel extension.

Upon closing, the bolt passes through the slots cut in the front of the barrel

Gun barrel

A gun barrel is the tube, usually metal, through which a controlled explosion or rapid expansion of gases are released in order to propel a projectile out of the end at a high velocity....

 extension, and then rotates; at this point it is locked in place.