Box Fan Filter Mounting System

Wanted a minimal clip system for my cheap 20x20 box fans from Walmart or similar. Replaces the rear fan guard and the mounts will screw into the existing holes. Will hold a 20x20x1 filter

Two types of mounts. The clips are for easy removal of the filter, but don't provide a real positive hold of the filter. The hooks will surround the filter better, but the filter has to be slotted into place.

I prefer to put the hooks on the bottom of the fan, and the clips on the sides and top. That keeps it pretty well locked in. Depending on how you have your fan located, changing those positions may be helpful.