Spannbettlaken

A Spannbettlaken - this is the long german word is amused me - and it really define that this thing supposed to do - to tense a sheet on to bed.

I've reverse engineered it from IG link below that appears useful for me
https://www.instagram.com/reel/CXvWSy0JkgP/

A designer of the thing failed to provide suitable link to shop. So I got this thing using my imagination and Fusion360. I've provided a drawing in archive, next to stl files, so please feel free to change it at your pleasure.