Depending on the direction in which you clip this to the top of the door, either it just sits there doing nothing, or it prevents the door from closing all the way. This is very useful if you have a small child you need to keep an eye on but they've figured out how to operate the privacy lock on a bedroom or bathroom door.

I used Hatchbox True White PLA on an Ender 3 Pro with a 0.8mm nozzle, the Cura "draft mode" 0.32mm profile, supports, and a brim—but this is not a complex print and you can certainly print it other ways.

The mildly clever thing about the design is that you can adjust it using side cutters to fit doors ranging from 32 to 36mm thick. If your door is not within that range, you can try scaling the model.