We just had work done in our living room, and the large (a little over 1'Wx2'H) air return vent grille was removed. I just painted it to match the wall. The air return vent is in an upper corner of the living room wall, at the ceiling. (Our house is around 1970 vintage.)
The grille is metal and has angled slats. Should the slats be angled up toward the ceiling? Or down toward the room? Or doesn't it really matter?