This is a corner bracket for the Anet A8. It was taken directly from the .dxf files of the Anet A8 monolith frame (https://www.thingiverse.com/thing:2094209 - many thanks for uploading this and taking the time to design it.) I extruded it in Solidworks to be the same thickness as the acrylic stock frame.

It has a slightly smaller profile than the original bracket but fits perfectly with the stock frame, no changes needed. I used this to replace my broken stock bracket.

This works on both left and right sides of the original frame.

Update I uploaded the wrong .stl file that was 5mm thick instead of 8mm thick - the correct file is now available to download.