ACommercial bookcases come in four height ranges: low (36–42 inches, 2–3 shelves) for under-window placement or room dividers; mid-height (60 inches, 4–5 shelves) for general use without wall anchoring; full-height (72 inches, 5–6 shelves) which is the most common commercial configuration for maximum storage; and high-density (84–96 inches, 6–8 shelves) for libraries, storage rooms, and law firms — always requiring anchoring. The 72-inch full-height unit is the standard commercial choice. Mid-height 60-inch units are selected when wall anchoring is not feasible or when sight lines must be preserved.