The Shelves of Infinity, also known as Unit Zed-X4-one-9, was a piece of furniture created by the Assemblers on Generios 8. It was said to be their greatest achievement. It was one of the Three Great Treasures of Generios.
What was so special about the Shelves was that the pieces (which kept appearing and disappearing) were able to exist in multiple dimensions. The instructions also kept getting longer.