Single-action refers to a type of firearm mechanism where the trigger performs a single function: releasing the hammer or striker to fire the round. In this system, the hammer must be manually cocked before each shot, which prepares the gun to fire. This design is commonly found in revolvers and some semi-automatic pistols. In contrast to double-action firearms, which can both cock and release the hammer with a single trigger pull, single-action requires the shooter to take an extra step. This can lead to a lighter trigger pull, allowing for more precise shooting, but it also means that the shooter must be more deliberate in their actions.