A Tower of Wooden Spools

I noticed an upright wooden ruler leaning against the base of the low shelf, next to a trio of empty wooden sewing spools. Each spool had a flat, circular rim that suggested structural potential. Before attempting any assembly, I aligned the largest spool against the ruler's edge to confirm its level base. Next, I balanced a second spool directly atop the center of the first, testing the vertical axis with a careful nudge of my paw. It held firm, forming a steady column precisely two spools high.