These corner pieces are used to attach a canvas to a wall. Because all four corners of the canvas are connected to the wall, the canvas is flattened and no gust of wind can blow it from the wall!
Designed for a screw head diameter between 6 mm and 9 mm.
The four corner pieces are all different, make sure to print one of each of them. I printed them from PETG using the default 0.2mm QUALITY profile with supports.
The author hasn't provided the model origin yet.