A boring air register story
Deja vu moment. I accidentally smeared paint over my air register in my bedroom a couple of years ago, so I went to Home Depot and had the exactly same problem! It ended up taking two trips...
Back to present. So I bought 14 x 8 air grille and came back home. Of course I was off by 2 inches on both sides! So second trip to Home Depot was done then. I got 12 x 6 instead, and it fit!
A duh moment upcoming now. I read the words on the label...it said it is for duct size of 13 7/8 by 8 inches... oh! Why do they like to confuse me!