and firing pin in one piece, they are generally considered to be mechanically simpler but are more robust in construction than a typical firing pin. Many small calibre rimfire bolt action rifles and some centerfire automatic weapons (e. g., vz. 58) may appear to have a striker-operated firing mechanism but are actually a type of linear hammer. The hammer can be likened to that of a pile driver and is mainly contained within the bolt. It is much like the striker already described except that the "hammer" upon which the firing spring acts and the firing pin are separate units. Confusingly, parts lists will often refer to this type of hammer as a "striker". Striker-fired (or similar) bolt action firearms may be classified as cock-on-close or cock-on-open. Cock-on-close When the breech is opened and retracted rearward, the striker is also carried rearward so that the striker catch passes over the trigger sear. When the bolt is pushed forward to close the breech, the striker catch is held by the trigger sear. The firer must close the bolt with sufficient force to overcome the force exerted by the cocking spring. Notably, the Lee–Enfield and Belgian Mauser cock on closing as do many small calibre rimfire bolt action rifles. Cock-on-open The breech of a bolt action rifle is opened by first rotating the bolt handle. In cock-on-open operation, this rotation acts on a cam (similar to the action of a screw thread) which retracts the striker, compressing the cocking spring and holding it there. When the cocking handle is rotated closed, the cocking cam disengages but the striker is retained in the cocked position by the trigger sear. Introduced in the Mauser Model 1871, it significantly reduced the risk of accidental discharge upon closing. The system of operation was widely adopted and is used almost exclusively in modern centerfire rifle designs. The Mauser Gewehr 98, the Mosin–Nagant and M1903 Springfield are examples of service rifles using this type of operation. Other applications Modern era guns in general (and not just firearms) use a firing pin of some description to initiate firing. Mechanical contact fuzes in explosive ordnance will employ a firing pin or striker to initiate detonation. Such devices include: artillery projectiles, aerial bombs and land mines. In landmines, non-metallic firing pins, made from ceramics for example, may be used to minimise their magnetic signature. The M127A1 signal rocket (and other similar