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

furnace filter slot cover
➡️【Mk.com】✅खिलाड़ी मुफ्त स्पिन, ✅बोनस नकद और यहां तक कि जैकपॉट भी जीत सकते हैं। लकी व्हील ऑफर को अन्य कैसीनो प्रमोशन से अलग करने वाली चीजों में से एक है... ✅ 

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

Magnetically attaches to ductwork to cover furnace filter slot door Two-piece design works with any 1-inch furnace filter up to 25 inches long Universal one-

furnace filter slot cover slot, these are not provided with this product For an option with removable channels for multiple filter sizes, see our FRB filter rack base; Come in a

kuy 138 slot The issue is an open furnace filter slot In other words, the slot has no cover and you can see the spine of the filter A quick look at