That works too, though IIRC the common procedure in the industry in my country is to use a warning label/shield and hang it on the breaker box during repairs, l

That works too, though IIRC the common procedure in the industry in my country is to use a warning label/shield and hang it on the breaker box during repairs, locking the breaker box itself, then short out the circuit to ground and measure to be sure. Locks on the breaker itself are more rare (usually for low voltage repairs where the common person might frequent the area)