Rule 35 of 40 · Chapter VI — Tools, Habits, and Judgement
Use tools rated for the voltage
Why this rule exists
An insulated screwdriver and a 1000 V glove earn those ratings by test, and a tool without them is guessing at your expense. Worn insulation can flash over or conduct at voltages it was never built for, putting current into your hand. Meters carry a CAT rating, CAT II, III, IV, for the transient energy they can safely handle at that point in the system; use a low-category meter on a high-energy service and an internal arc turns it into shrapnel. Rated tools are not optional. They are the barrier between you and the circuit.
In practice
Match every tool to the job's voltage and energy: insulated (1000 V rated, individually tested) hand tools for work near live parts, gloves of the correct class, and a meter whose CAT rating meets or exceeds the location, CAT III or IV for service-entrance and panel work. Inspect insulation before each use and retire anything nicked, cracked, or worn to bare metal. Use meter leads rated to the same category with finger guards. Keep the right tool for the voltage on hand so you are never tempted to make do with the wrong one.
When it doesn't apply
Ratings assume the insulation is intact and the tool is used as intended; a rated tool with damaged insulation offers no protection and false confidence, which is worse. When the voltage or available fault energy exceeds your tools' ratings, that is your signal that the job needs different equipment and likely a qualified worker.