Circuit breaker locks are designed to lock a circuit breaker switch into the off or on position. The switch will remain in that position for as long as the lock is installed. Once the lock is removed, the circuit breaker can then be engaged and turned on or off.
These locks are an essential part of lockout tagout procedures because they help effectively isolate sources of hazardous electrical energy. They also come in different sizes to accommodate circuit breakers of differing voltages.