Originally Posted by Bama Rambler
I agree with everything Cowracer said. It's standard practice to break the positive side here in the US.
Yes it is the standard practice, even if it doesn't make as much sense as breaking the ground circuit. However, every auto mechanic knows to disconnect the battery ground strap
before removing engines or trannies. That, too, is standard practice.
I'd break the circuit with the single wire. Some trailers have two or three wires attached to the positive post. On those it makes more sense to switch the ground circuit (single wire).