A shotgun shell is a self-contained cartridge typically loaded with multiple metallic "shot", which are small, generally spherical projectiles. Traditionally lead was used, but increasingly steel, tungsten or bismuth shot has replaced lead, due to laws designed to protect the environment. A single, large projectile known as a shotgun slug can also be used, and numerous specialty rounds such as less-lethal rounds (i.e. beanbag rounds), flechette rounds, lead-dust rounds for door-breaching are also available. An old non-lethal shotgun load consisted of a shotgun shell loaded with rock salt, which could inflict very painful, but rarely deadly, wounds, and was therefore popular for scaring away trespassers.