Safety Selector
Also: Safety
The control that blocks the firing mechanism to prevent an unintended discharge. On a bolt rifle, often a two- or three-position lever at the rear of the bolt.
A safety selector mechanically blocks the rifle from firing, usually by interrupting the trigger or pinning the firing pin or sear. On many bolt actions it is a thumb lever near the rear of the action. A three-position safety is the precision favorite: one setting is fire, the middle locks the trigger but lets you cycle the bolt to load or unload safely, and the rearmost locks both trigger and bolt.
A safety is a mechanical aid, not a substitute for muzzle discipline. It can fail, and it does nothing about where the gun is pointed. Keep it engaged until the sights are on target and you have decided to fire.