I love these MAX7219 4x1 modules! They are so cool to join together to make into scrolling marquees. But if you've worked with them you know getting them to line up correctly is a bit tedious. Once they're soldered together they KINDA stay put, and the double-wide case linked above does a pretty good job once you have it assembled.
But I wanted something more, so I designed this series of snap-fit connectors to join MAX 7219 4x1 modules together. The clips have pegs which snap into the holes on the modules. You'll print one for the top and one for the bottom. The nice thing about these clips is you don't have to use screws and even if you remove the clips later they are really nice for getting them spaced correctly for soldering.
I did three different clip versions: A plain one, a version for mounting to MakerBeam/OpenBeam 10x10 extrusion, and one with a pair of 3mm eyelets for mounting on a board or affixing to another type of extrusion (i.e. if you want to mount it to the top of your printer or something).
These clips have really tight tolerances and they will be hard to click into place initially, but that's by design. They need to be really tight to keep the displays together. I would recommend taking a thin steel ruler and running it between the clips initially to break away any ooze that might have set up between the pegs during printing, and to loosen the plastic up a bit to be ready for inserting.
You should print with 0.1mm layer height and relatively slow. DO NOT print with 100% infill. If you do the clips will be so stiff you'll never get them clicked in. I used 25% and they worked just fine. Just keep in mind these were designed to be secured once and left in place. They're not designed to be removed and reinstalled a dozen times, and if you do they'll probably crack and fail.
The only part which needs support is the MakerBeam/OpenBeam part (interior cavity). Other than that everything prints without supports.
Since the base of these models is thin you'll want to make sure you have good bed adhesion. I use Blue Painter's Tape and tweak my z-height and it works great.