The highest and best use of 3D printers is building accessories for 3D printers.
When I first dipped my toe in this hobby, I laughed at photos of people with their extensive collection of filament spools. Now, I find myself running out of desk space and need a shelf for my... filament spools.
READ THE INFORMATION IN "PRINT SETTINGS" or you'll be setting yourself up for failure. There are pitfalls in this print due to the amount of stress the brackets must tolerate.
There are three different bracket styles: Left, Center, and Right. For a one-meter long shelf, I printed two Center brackets and, of course, one Left and one Right. They support a PVC plastic pipe, and the spools rest between the pipe and the wall.
PVC pipe does not have a well-defined diameter! I chose this polished, black pipe from Amazon (not an affiliate link). It is nominally 3/4", but the outside diameter is 1.05". If you want to use pipe with a different OD (it still might be labeled 3/4") you'll need to use FreeCAD and change the size of the pipe slots.
The screw holes are designed for #10 screws that go into hollow wall fasteners. If you use smaller screws, be sure to use washers or the screw heads will pull through the brackets (even if you resize the screw holes first).
Anyway, the key point is not to try to print these vertically. They were designed so each part has a flat side that can go against the raft without needing much in the way of supports. If you print them vertically, the brackets will separate along layer lines when you load the shelf. Your precious spools of PLA will crash down on your printer and both printer and spools will be destroyed, and I will not be responsible.
If your slicer likes to re-orient the parts, you should move them back so that they print as they are shown in the preview renderings above. Avoid heartache: don't stress your layer lines!
In general, this design stresses the limits of PLA. Overloading the shelves or using inferior material or having your printer settings wrong all will lead to failure. I will probably end up re-printing these in ABS after I've destroyed my machine and a few spools of filament.
The flange extensions on the Left and Right parts keep the whole shelf from wobbling when not loaded. The slot configuration for the lower screw prevents stress on the brackets if your screw holes aren't perfectly spaced. It took several iterations of the part and almost a kilo of filament to finally get it right, so modify the design at your peril.