this is an example of the twist and lock system, by harry thaler. the images below show some close-ups of how it works.
...a system that allows the user to lock special crates together in order to create different combinations according to the desired needs. users can apply the system in different ways, for instance, as a book or wine shelf.
i like the idea of being able to reconfigure your furniture as you wish, and i really like the coloured components of this modular system too.