This is a simple solution to put a Milwaukee fan on our Packout Systems. I was sick of it sliding around and not being safely on top of my boxes.
The fitment is, in my eyes, okay. It will not fall out of your boxes but can be easily slid out again. However, it's important to note there's no latch/spring that keeps the fan in place.
On the bottom of the fan are 4 rubber pads. You can easily remove them with pliers or something sharp; they are only pushed in. After that, place the adapter on it with the straight edge of the feet towards the front, where the knob/battery is. Then, use 4x M6 screws with at least 20mm length and screw them into the holes where the rubber pads were.
4x M6x~20mm Screws
The feet are designed by "joshl_1995" https://www.thingiverse.com/thing:5187130.