Hi! I'm not sure where I messed up, but the meshes I made for the brackets look odd, as in the places I marked here: 
I've tried fixing the normals, then deleting the faces and filling them in again, but it hasn't worked. Can't think of anything else that would fix it.
Anyone got any idea what I may have done wrong?
Sure! Here's the google drive link: https://drive.google.com/open?id=1kEjd5cDEUeSi05s_LFs47nWb77FoYcga
Hi galowglas, your Angle field in the Auto Smooth is greyed out. This is because there is some 'Custom Split Normals Data' on your mesh. Don't ask me what that means, I have no idea. That sounds more like something @jlampel would know...
Anyway, remove that data:
Then you can Shade Smooth with Auto Smooth again.
I also noticed that you have some broken quads (meaning that the four vertices of a quad do not lie on one plane).
I'd recommend fixing that, because that also gives shading artefacts.
Enable the Loop Tools addon, that comes with Blender. select the Faces that should lie on one plane.
For Left Click Select: right click, for Left Click Select: press W to bring up the specials menu.
Loop Tools > Flatten.
I have no idea why the model has custom split normals in this situation, but spikeyxxx 's solution is right on the money!
