My furnace has two 1 filter slots Should I use both slots?

FilterLock satisfies the department of energy recommendation that the furnace filter slot be covered to avoid air leaks; Click here to learn more about Eco

filter housing slot, thus allowing you to slide the filter in with ease Once installed, the air filter does not completely cover the vent or

furnace filter slot to locate your furnace air filter location for easy filter replacement Look for a long, narrow slot with a removable cover The filter

777 slot free FilterLock satisfies the department of energy recommendation that the furnace filter slot be covered to avoid air leaks; Click here to learn more about Eco