Watch the reshelving cart complete one full circuit of the stacks and it becomes clear the route is never the shortest one available. It follows the aisles in the order set by call number, not by geography, doubling back past ranges visited an hour earlier because the alphabet insists on it. Three or four shelves, canted slightly to keep the spines from sliding, sit at heights suited to an average adult who does not, in practice, exist; the top shelf serves the tall staff, the bottom serves almost nobody comfortably, and the whole apparatus turns on four casters, one of which develops a signature squeak after roughly eighteen months of service, arriving almost precisely with the cart's first worn wheel bearing.
The squeak becomes a kind of location beacon. Patrons three ranges over learn to associate it with an approaching restock and adjust their browsing accordingly, stepping aside before the cart rounds the corner, the way a sidewalk clears for a delivery truck not yet visible. Staff learn the sound of their own cart specifically, distinct from the others working the same floor.
Loaded, a cart can carry forty to sixty volumes, its frame flexing almost imperceptibly under a full run of hardbacks, though the wheels tell a different story after a few thousand circuits. Empty, it is wheeled back to its dock near circulation and left there, angled slightly off the wall, ready for the next hour's returns. Tomorrow it will make the same circuit, in the same order, a route dictated by call number and answerable to no one.