Warning: this may well be the stupidest question anyone will ask you this week.
Pretty much every medicine cabinet I've ever had came with glass shelves that were smooth on one side and sort of pebbled on the other. I just installed a new one in my master bath and, when I went to put the shelves in, it dawned on me that I had no idea which side went up. My gut says smooth-side-up, but the ones in the guest bath are smooth-side-down. (They may well have been that way since I bought the house in 1979.) And I cannot for the life of me remember which way the old ones were when I did the demolition a week ago.
Is this one of those meaningless pseudo-religious things like how toilet paper goes on the holder?