Many times the actual cutout in drywall is smaller than the "vent" cover, which is mostly for aesthetics. So of course you can make a vent cover two feet long

Many times the actual cutout in drywall is smaller than the "vent" cover, which is mostly for aesthetics. So of course you can make a vent cover two feet long with only the center 50% being the actual vent and the rest being a thin plate that simply sits on the wall and hides the screw holes.