RimWorld Shelving Efficiency: 3 Stacks per Tile, Aisles and What Never Fits (1.6)

How much a shelf really holds in RimWorld 1.6, and how to lay out a storeroom that haulers can still walk. A shelf holds 3 stacks per tile: 6 on the 2x1 shelf, 3 on the small shelf, 1 on bare floor. Covers stack limits, the real path cost of walking over shelves, the two-deep-plus-aisle layout (144 stacks in a 9x9 room vs 81 on the floor), what shelves refuse (chunks, minified furniture, toxic wastepacks, corpses of body size 0.75 or more), why shelves stop deterioration but not rot, and three reasons a shelf stays empty.