I have this file. No Idea what I did to it but when I try to apply color to the piece at the origin it colors only one or two faces.
The other piece will color the whole thing.
They are both grouped.
They were not always in the same file.
The first piece and a mirror image piece in a file do the same thing.
I created these piece and used them in an assembly file. I took the good one from that assy file.
Corner Brackets.skp (1.9 MB)