Выражение встречается в следующем контексте: The Cardinal Safety Rules were written to provide clear communications to all employees about the importance of sustaining a safe workplace for all Manroc employees through safety-related work behavior. The rules below were chosen because a breach of each one has the potential to result in a critical injury or fatality. Standard Accident/Incident Investigation protocols will be followed upon a breach of these rules. It must be clear to everyone at Manroc work sites that failure to observe these rules will result in the dismissal of the employee(s) or contract worker(s) involved.
1. Unauthorized removal of a personal danger tag and/or lock in accordance with our lock-out procedure.
2. Failure to place a personal tag and/or lock where designated in accordance with our lock-out procedure.
3. Unauthorized blasting, including blasting before clearance of the “tag-in” board and improper guarding during blasting.

Я не совсем понимаю смысл слова lock и tag в данном контексте и получается при переводе бессмысленный набор слов.