Just a simple corner mount for a 3mm mirror or plexiglass or anything like that.
I made this just because my gf bought an Ikea-like mirror without mounts that was supposed to be glued to something and I didn't really wanted to glue anything to a wall.
The space is 3,5mm so it has enough space for either a screw head or a nail without an unnecessary gap between the wall and the mirror.
Designed to be easily printed.
In my case, the 4th upper corner is just there for aesthetics, it doesn't hold anything.
Print time around 10 minutes per piece.