Inventory
Warehouse Slotting: Put the Fast Movers Where the Feet Are
Travel is most of the time in a manual pick operation. Slotting is the cheapest lever on it — no new equipment, no new system, just moving stock to better locations.
In a manual picking operation, walking accounts for the majority of the picker's time. Not scanning, not lifting — travelling between locations. That makes location assignment one of the highest-return improvements available, and unlike automation it costs almost nothing but effort.
The basic principle
Fast-moving items belong closest to the despatch area and at the most accessible height. Slow movers go to the far aisles and the high and low shelves. The ranking that matters is pick frequency — how often an item appears on an order — not sales value and not physical volume.
This is a different ranking from ABC by value. A cheap consumable picked forty times a day belongs in the golden zone; an expensive item picked twice a month does not, whatever its classification for inventory management purposes.
Slot by how often it is touched, not by what it is worth.
The golden zone
Roughly waist to shoulder height requires no bending or reaching, and picks from it are faster and safer than anything above or below. It is scarce space and it should be allocated deliberately to the highest-frequency items rather than by whatever happened to be put there.
Beyond frequency
• Affinity — items frequently ordered together should be adjacent, even if one is slow on its own.
• Weight — heavy items low, and early in the pick path so they sit at the bottom of the tote.
• Cube — bulky items need locations that fit them without blocking the aisle.
• Sequence — the pick path should flow one way through the building, with no doubling back.
• Segregation — hazardous, temperature-controlled and high-value stock have constraints that override optimisation.
Measure before and after
Capture picks per hour and, if the system supports it, distance travelled per order line, for two weeks before you move anything. Without a baseline the improvement becomes a matter of opinion, and the effort of re-slotting will not survive its first challenge.
Re-slot on a cycle
Demand mix drifts continuously — seasonal ranges, new products, discontinued lines. A layout optimised once decays within months. Review the frequency ranking quarterly and move the items whose class has changed; it is a small amount of work if done regularly and a large project if left.
Bring the pickers in early
The people who walk the building know things the data does not: which aisle congests at 10am, which location is awkward with a pallet truck, which two items get confused because their packaging is identical. A slotting plan built purely from a frequency report and imposed on the floor will be quietly worked around within a fortnight.
Slotting by pick frequency got us a genuine double-digit productivity gain with zero capital spend. It took two weekends of moving stock and a week of grumbling.
The affinity point is underrated. Two items that appear on the same order constantly should be near each other even if one is a slow mover on its own.
Re-slotting quarterly rather than once is what sustains it. Ours decayed within six months as the product mix moved and nobody had ownership of the layout.