This is an adapter for holding sandpaper with an oscillating multitool. I designed it for a DeWalt DCS356, but it may fit other brands/models with the same blade interface.
The Everclamp grid with sqwasher plate and thumbscrews lets you attach sandpaper, a sponge, or other irregularly-shaped object...
In other news, if you try to upload a file named uncalibrated_example.stl to Thingiverse, it fails with no error message, because somewhere they have a pr0n filter searching for rated*x.
Some people might find this bundle_scad.py code useful. It combines an STL, SCAD, and all its dependencies into a single file.
I don't know how to tell you this but this already exists. Get a Oscillating Multi tool pack at the store and it comes in all of them. I have three different ones.