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.
That is interesting. I'm professionally curious about the drive mechanism for the oscillation pattern on these now. As a former auto body shop owner and painter, I would not expect this to be free of mechanical error like a high quality pneumatic dual action sander, but it is an interesting idea. In fact I can imagine taking this to another level and creating a thin sanding blade like design with Emory paper, to use in very tight slots.
You can buy these from Dewalt with triangular shaped velcro backed sanding pads. I used one to refinish a crappy bedside table during covid and it did leave a lot of weird sanding marks (especially if the paper picks up any debris) but it does work. It's probably better suited for small surfaces that aren't flat.
It does matter for automotive-class perfection. You will have hot spots develop that dig deeper than the rest of the surface. We are talking about mirror gloss perfection though. You are likely not working on a project of this scale/class.