The Master Lock rotating electrical plug lockout is a thermoplastic shell that surrounds an electrical plug and combines with a padlock (sold separately) to help protect against plug connection during maintenance and repair, and fits electrical plug sizes up to 3" diameter x 6" (7.6 x 15.2 cm) with a cord diameter of up to 3/4" (1.9 cm) (most 220v and some 550v plugs). This lockout consists of two halves; one slightly smaller half fits inside the larger half when not in use, for installation in confined spaces and a compact storage footprint. Where the two halves meet, flanges from each half align to form two locking holes. A padlock shackle placed through these holes obstructs the inward rotation action of the lockout, helping to prevent access to the plug. Two locking holes provide the ability to require multiple authorizations to allow connection of a locked out plug. Red thermoplastic is electrically nonconductive and functions in temperatures from -50 to 350 degrees F (-46 to 177 degrees C). Three (English, French, and Spanish) warning labels with rewriteable areas for task-specific details are included. This lockout device is part of a lockout/tagout (LOTO) safety procedure required at facilities where electricity sources 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.