Here I have three slightly different Cabinet Hanger inserts for you.

Instructions:

First you need to drill a 20 mm wide and 9 mm deep hole to put them into.

Then you push (or screw) in the Inserts.

After that step you can use a 3 mm screw to lock the hanger in place.

Then use sth. like a 4 or 4,5 mm Screw as a counterpiece to hang your project on to.

Sth. about the three different versions:

Springy: Slightly overengineered: Idea is to have more even tension.

Spiky: Barbs to generate more friction.

Twisty: Screw the Insert into place with the Key (included in the .stl). With Twisty it is necessary to drill the 20 mm perfectly to the desired depth. Otherwise it is hard to align it correctly.

If you have any questions don't hesitate and feel free to post them in the comments.

Have fun and keep printin!