The lock of a firearm is the mechanism used to initiate firing. It is a historical term, in that it generally refers to such mechanisms used in muzzle-loading and early breech-loading firearms. Side-lock refers to the type of construction, in which the individual components of the mechanism are mounted either side of a single plate. The assembly is then mounted to the stock on the side of the firearm. In modern firearm designs, the mechanism to initiate firing is generally constructed within the frame or receiver of the firearm and is referred to as the firing or trigger mechanism. Hand cannon Hand cannon, the earliest of firearms, had arrived in Europe by 1338. These cannons were loaded from the muzzle. The propellent charge is lit through a touch hole. A small priming charge over the touch hole is ignited with a lit piece of slow match or similar. These hand cannons were ungainly: the difficulty being in holding and aiming the weapon while manipulating the slow burning fuse needed to fire it. Improvements to the basic design placed the touch hole and a priming pan (flash pan) to the side of the barrel. A cover to the priming pan allowed this to be filled with priming powder in advance of firing but there was no actual mechanism for firing. Firelock A firelock is a firearm in which the priming is ignited by sparks. More specifically, it refers to the mechanism or lock of such firearms. It may also refer to a gun's lock which uses slow match to ignite the powder charge. The matchlock was a lever mechanism that simplified the ergonomics of firing. Slow match would be held clear of the flash pan in a spring-loaded pivoting arm (the serpentine). Depressing the firing lever would dip the burning match into the flash pan. The snap matchlock latched the serpentine back against spring tension. Actuating the trigger or firing lever would release the serpentine, allowing it to rotate and dip the lit match into the priming pan. This reduced hesitancy at the moment of firing and thereby improved accuracy. However, rather than firing, the match might be snuffed out when it struck the flash pan. The next advance was a self-igniting firearm that did not require a lit slow match to fire. The first of this type is the wheellock. The wheellock produces a spark in much the same way