I started off going to call this a thumb-nut, then I switched a screw head then back to a thumb-nut. It's a little plastic cap that goes over a screw head. It does two things. One, it makes it easier to twist the screw by hand. And two, i'm going to use them on my astronomy equipment and make them out of glow in the dark PLA. Everyone always loses hardware in the dark. it just happens.

The STL is dimensioned for a 7mm screw head, but I've included the CAD file so you can make what ever size you need.

To be used with:

https://www.thingiverse.com/thing:2990278

and

https://www.thingiverse.com/thing:3040945