This is a "Virtual Bookshelf" that serves as a place to keep "parts" in virtual space, during a CAD design process. Its not meant to be printed in the real-world.
When designing in 3D space there are always copies of the different parts (primitives) or versions of a design that we set off to one side. Usually they radiate out from the central design area at 45 degree angles, from the older nearer to the newer farther versions. They're just copies of the part at stages of development process, saved so we can go back to any particular point in the design process to start over from that point. This helps us keep track of how features develop and change during the iterative design process. Scale it in any direction to fit your space.
One of the easiest thing to do is put these parts on a virtual shelf. You can put labels on the shelf if you want but parts related to a specific design are usually clear. I orient them on the virtual shelves from previous versions of the left (older) to newer versions on the right.