Review on 🧲 Master Magnetics - B005HY9KDM Magnet Sheet, Magnetic Paper, 12x24 inches, White Vinyl Backing, 08505 by Karla Richter

Purchased to block air flow on a return air grille for a domestic oven. During the summer when your furnace is working as a central air conditioning fan, you sometimes need to turn off certain return airflows to maximize your system's efficiency. In my case, it is necessary to block the return of cold air to the basement so that I suck warm air from above for cooling and not cold air from the basement. In winter, the opposite is true, which is why you need the opportunity to unclog. I've been doing HVAC for years and we used this trick. The sheet of magnetic signage material can be cut to cover exactly what you need on each steel air register. You can easily attach or remove it according to seasonal needs. Looks great and works great.