Circuit breaker lockers, also known as circuit breaker locks or lockout devices, are used to ensure that a circuit breaker remains in a specific position (either on or off) to prevent accidental switching. This is crucial during maintenance or repair operations to ensure the safety of personnel by preventing unexpected energization of the circuit.

These devices are part of a broader approach called Lockout/Tagout (LOTO) procedures, which are designed to safeguard employees from hazardous energy releases while they perform service or maintenance on machines and equipment. LOTO procedures typically involve several steps, including turning off the machine, isolating it from its energy source, and applying lockout devices to prevent the machine from being started up again until the maintenance or repair work is completed.

Circuit breaker lockers are available in various designs to fit different types and sizes of circuit breakers. Some are universal, while others are specific to certain models or brands of circuit breakers. They usually work by physically blocking the movement of the circuit breaker's switch, thereby ensuring it stays in the desired position until the lock is removed, which should only be done by authorized personnel.