The model is a protector for the corners of any sheet material. There is a cutout on the inside corner to protect the delicate corners.

The model is parametric it is easy to modify in the Fusoin 360 file:

Sheet: The thickness of the sheet.
Gap: A gap between the sheet and the protector. It is for some soft material glued to the inside of the protector, like felt.
Wall: The thickness of the wall of the protector.

There is generated models for 18 mm sheets and 0, 1 and 2 mm gaps.