Isolating energy sources with personal locks and tags, then verifying isolation before work.
Lockout is a sequence: prepare, shut down, isolate, apply your lock and tag, release stored energy, then verify isolation before starting. Verification means trying the controls and testing for absence of voltage with a meter proven on a live source. Capacitors can hold a charge after the power is off. The Canadian Centre for Occupational Health and Safety publishes a plain-language guide to the steps.
Source: CCOHS OSH Answers: Lockout/Tagout
Exam work areas
A · Safety and trade practice