Use at your own risk!
I was challenged to design a 3D printed cleat to hang the Milwaukee Packout system on the wall.
I'm still not convinced that a 3D printed part is strong enough, but I printed the cleats in PET-G and they seem strong enough for light use. When I've tried pulling the box away from the cleats, the box bends more than the cleats.
I've only tried the cleat on the half size boxes so far but they should work with the full sized boxes.
Update: 20190311: I added the Fusion 360 archive files if you want to see how these were made.
The easiest way to align the cleats it to insert them into the bottom of a case and cover the cleat with double sided carpet tape. Then stick the Packout box where you want it to hang. When you slide the box off the cleats the cleats should stay in place and you can permanently screw them in.
To install the latch catch, slide the box fully onto the cleats and tape the catch against the latch. Carefully remove the Packout box and screw the latch catch in place.