These brackets have been primarily designed to fasten a white-board to the wall. I made the design parametric so it's easily customizable to wall-mount any kind of frame, painting, screen, tablet, etc.. There are now 2 FreeCAD files. One is for a plain bracket, the other is for a pivotable bracket for a quick remove of the frame from the wall. To adjust the dimensions, open the desired FCSTD file with FreeCAD, then the 'Dimensions' spreadsheet in the tree view. You can have both the design and the parameters side by side by clicking on the 'Windows' menu then 'Tile'. Once you are satisfied with your settings, export the new thing in STL. When some parameters combinations are impossible, FreeCAD will either ignore your choice or just crash. I provide STL files as examples. This is an open-source design. FreeCAD files are provided. Feel free to modify this thing at your convenience. Good design is hard work, even small donations are welcome.