Lattice Shelf Brace
This is an overkill industrial looking shelf bracket. It is designed for planks of 165 x 7 mm, in my case a piece of floorboard. The mounting hole screw hole size is 3.5mm, the screw driver access hole size is 6mm.
In case these sizes are not what you need I provided the SolidWorks file, feel free to customize it for personal use.
Printing notes: I printed them twice (Once mirrored in the slicer). For overkill strength (which I did) I recommend having wall thickness of 4, with a nozzle of 0.4mm, by doing this the braces are solid. Except for the intersections and the plank side mounts. Using this setting uses a lot of PLA tho ca. 100g per bracket. I'm pretty sure that one bracket could hold like at least 50kg. I couldn't get it to flex/bend.




















Un-pro tip: Mirror one of the brackets so you have a left/right set. Also, if scaling the brackets down to less than ±10 inches, make sure you either have a screwdriver small enough or extension that can fit through the pre-modeled holes - otherwise you'll need to enlarge the screw holes (in model or post-process) for tool access to fully engage the top screw since the triangular webs may be too deep for you.