These rules were outlined by the legendary Col. Jeff Cooper, founder of Gunsite Training Center in Paulden, Arizona. They are widely held as the defining rules within the industry, though the NRA and other entities have their own which are worth reviewing as well. Feel free to share this graphic to spread the gun safety love!
Never let the muzzle cover anything you are not willing to destroy. (For those who insist that this particular gun is unloaded, see Rule 1.)