Good home-repair question — answering as the UphillTech team:
The ground pin is usually facing down, and, if I recall correctly, when I installed some tamper-proof receptacles recently, the printing on them was right-side-up with the ground pin down. I believe it's also a requirement in some localities. On the other hand, people supposedly install the ground pin facing up as a safety precaution: if you're falling or dropping something onto a plug that's not securely plugged in, you'll hit the ground pin first so there's no risk of a shock. If you've got both orientations within any one room, it's possible the installer didn't know what he was doing. If...
Full answer by Niall C.: https://diy.stackexchange.com/a/8231 (CC BY-SA 4.0).
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