By the sounds of it KoN probably the only sure place would be on the + and - terminals of a battery.
Don't think there is anywhere that is purely positive or negative. By the way, just a suggestion for everyone, if you dont respond to a wind up merchants postings he will probably get fed up with talking to himself so just ignore him. Responding to his words is pointless.
I know the last bit is not related to this thread but I thought I would slip it in.