If you downloaded and printed any of the Prusa topper decoration objects available here, you already know what this is good for.

I wanted to be able to print any object and fix it at the top of the Z axis.
So I cut one of the knobs and on meshmixer I did some cleaning and made it a slightly tighten fit.
Just print it by itself and super glue it to any object (of appropriate size, or not...).

The corners of the knob can be put to face the front of the printer. Remember that before attaching to an object.