Update 3: The v3 “Slim” files. Final new version for now is a pair of new files, the “slim” brackets. I trimmed some material off that may not have been necessary, speeding printing and saving material. I thickened the bases to ½" for strength were it probably needs it. Probably best to start here.
Update 2: v3 provides a few new widths for 2x4s - 90mm fits some that I have, and 88mm fits some others I have. YMMV. The v2 is wider at something like 97mm wide. v4 may be modular (so different parts can be scaled separately in-slicer), and/or be made parametric (those features in my CAD software are beta ATM…). With a little slicing, you could probably save time and print 4 at the same time on a 256x256 build plate, but 1 at a time is safe. Flat bottoms are now the only variant available. If you want a bevel, just slice one off the corner.
Update: v2 replaces the original files - dimensions were off (problem of working on Imperial objects using metric, apologies!). New dimensions should be good, but should print a thin segment to verify, just like a cosplay helmet. The new file lacks the dummy 2x4s and includes 4 brackets, mirrored for convenience.
In addition, I've now added a variant with a flat bottom for no-support printing.
Original Description:
The model consists of a few dummy 2x4s (which can be split out and removed, unless for some reason you like them!) and the bracket. I'd suggest printing in PETG at a fairly robust setting(4 walls, 30% infill might be a good place to start), but I haven't printed or tested these. Mirror them for the other sides and you've got everything you need to build a shelf.
I'm not sure these are cheaper than the Yosemite brackets, but it looked like an interesting project to design something similar, and after all, why not?
Until tested, I'd be cautious about putting substantial load on them - They're certainly going to be decently strong, but almost certainly weaker than the originals. They can be beefed up, reinforced, and redesigned - feel free to remix and improve - I'm sure there's plenty I could do to both strengthen and simplify printing.
The author marked this model as their own original creation.