Carabiner
thingiverse
It's a carabiner, which I know there are already dozens of versions of, but this one is mine. The flat part is for adding text, which can be done via Tinkercad, or in PrusaSlicer (you have to download the alpha version for the text adding functionality).
Download Model from thingiverse
With this file you will be able to print Carabiner with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on Carabiner.