Koch’s square case can be oriented along either axis to adapt to storage needs. It can also be assembled into varying configurations. Image from Modern Danish Furniture.

Researching my latest book project, I cam across this modular shelf unit by Mogens Koch. The case can be oriented on either axis depending on storage need. And since the units are modular, they can be built up into multiple configurations. A stand and doors allow further customization. The cases are dovetailed, which surprised me a little, but it makes sense since these are made from solid stock. Here’s a group assembled as a wall unit at 1stdibs.