I think it's a personal preference for home's. In commercial places,
there is some belief if the screw becomes loose, pops out, and the
'metal' face plate falls, on a partially inserted plug, you can get a
spark that causes a fire. This sounds like a lot of "what if's", but
you need to do what you are instructed.
Personally I like grounds down, since the index finger has a habit of
migrating to one of the prongs, so best if it's the grounding prong.
tom @ www.mesothelioma-poll.com
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