Someone told me that on a 120 volt recpt. the ground is up for a metal cover and down for a plastic cover. Today I was installing recpt. in RS covers and I was told to put ground down. I've looked in ART. 406 and I can not find anything. Can someone help me out?
There was a great deal of discussion on this some time ago. Check through the archived posts. It is not an NEC issue. Either way is correct but if I remember correctly those who posted comments for "ground up" had better arguments than those for "ground down".
The search will show you a great deal of discussion, and a little deal of humor. Actually, the fastest way to get an answer is to look at the FAQ thread (the one at the top of the list in the NEC Topic Area).