This divider insert fits in the Dewalt "Tough Cases" and the new Craftsman cases with the dovetailed sides.
It extends far enough into the other side of the case to prevent parts from bypassing the dividers and becoming mixed.
The inspiration for this divider came to me the other day as I had some screws that I needed to take with me in my bag. I thought, wouldn't it be nice if I could just use some of the spare room in one of the cases I already had with me.
I have uploaded it as a customizer so you have the ability to dial in the fit, the dovetails can be a little fussy. I've include an STL that works for me in both style cases.
Since the part is so narrow, I printed this using a brim. I experienced some lifting off the build plate which definitely interferes with the fit of the dovetails.