thingiverse
I remixed this nice corner shelf to include holes for wall mounted screws. I also resized it to be a bit bigger to fit a speaker I wanted to put on it. Lastly, I carved a hole in the back of the shelf (in the corner) to allow passage of wires for the speaker. The dimensions of the shelf, back corner to first screw hole, then to the next screw hole are on the attached picture. Dimensions of the screw holes are the same on both sides.
The stl is oriented upside down so you don't need supports. The flat side goes up once printed. Mount the screws on your wall (level), place the shelf slightly above the screws and slide the shelf down onto the screws. 20% infill is plenty.
Direct link to the original creator's page
Click the "View on thingiverse" button above to visit the original model page on thingiverse. You can download the STL file directly from the creator's page for free.
This STL file is compatible with most FDM 3D printers (Creality Ender 3, Prusa MK3S+, Bambu Lab, etc.) and resin printers (Elegoo, Anycubic). Check the original page for recommended print settings and materials.
Yes, this model is available as a free download on thingiverse. Some creators accept tips or donations.
Most STL files can be modified using free software like Blender, TinkerCAD, or Meshmixer. Check the license on the original thingiverse page to see if modifications are permitted by the creator.