The Master Lock universal wall switch lockout covers both toggle and rocker wall switches and combines with a padlock (sold separately) to help protect against switch operation during maintenance and repair. This lockout installs over the switch plate, using the existing screws. Once installed, the hinged cover can be left open when not in use to allow normal switch operation. The locking hole accommodates padlock shackles up to 1/4" (6 mm) outside diameter. This lockout is made from a red polycarbonate for visibility and impact resistance, and the cover is translucent to show whether the switch is on or off. The lockout ships with two "DANGER" labels, one Spanish and English, and one French and English. This device is part of a lockout/tagout (LOTO) safety procedure required at facilities where electrical switches need to be isolated during maintenance and repair. Lockout/tagout (LOTO) safety procedures require that lockout devices meet Occupational Safety and Health Administration (OSHA) 1910.147(c)(5) standards for quality assurance. LOTO devices use color, warning labels or tags, and sometimes a physical barrier to help prevent machine operation or power activation during maintenance and repair. Master Lock manufactures padlocks, combination locks, and related security products. The company, founded in 1921, is headquartered in Milwaukee, WI.