The main purpose of Milwaukee's line of Packout storage ... bed: they're a bit unstable. Even if you have all of your Packout boxes linked together and placed in the corner of your truck's bed ...
I modified my truck bed to keep tools secure. The cover is made from 2×4’s skinned with 1/2-inch plywood. I bolted angle iron to the sides of the cover and secured the whole thing with eyebolts ...