Customizable Label Clip for Small Parts Tray

Clips for labeling small parts trays, e.g. [Customizable stackable screw box](https://www.thingiverse.com/thing:2222574) - default .stl files fit 2mm thick walls.

While uploading, I decided I'd better make this customizable, so I made a quick OpenSCAD version just now (originals were done in Fusion360). It appears to be working well, but let me know if you find a problem.

Variables:
Face Width: X-axis
Face Height:Y-axis
Face Thick: Z-axis
Fit Wall - Gap size that fits over your wall -