“This is a specialized version of the ‘Pluggable Containers’ thing: https://www.thingiverse.com/thing:4675184.
It lets you create different symmetrical pluggable containers in the openSCAD and thingiverse customizer.
These could be used as pill boxes, containers for cookies/gifts/, housings etc.
Please share your makes, because I would like to know what it is used for in the real world ;).
PS.: Since the thingiverse customizer seems to be broken right now I suggest that you download openSCAD version 2019.05 or higher from here: https://www.openscad.org/downloads.html and activate the Customizer in the ‘View’ menu. I have added a screenshot to the file sections that shows exactly what I mean.”