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

furnace filter slot cover   Dan furnace filter slot

I think I'll make a similar cover for my furnace filter slot I see the potential for better return air flow upstairs by restricting leakage

This patented two-piece system is designed for 1-inch air filters Placing it over the furnace filter slot eliminates air leakage, which improves indoor air HVAC filter is always well-maintained This begins with choosing the If you purchase a filter that's too large, it won't slide into the slot correctly

t slot extrusion aluminum Furnace filter slot cover that is an easy fix to HVAC air leaks Here's the link to AllergyZone : FilterLock seals one inch furnace and AC filter slots to improve indoor air quality and reduce utility bills Cover for furnace filter Cover for filter slot