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Put Walls: Sorting Batch-Picked Items Back Into Orders
A put wall sorts batch-picked items into individual orders without a mechanical sorter. Learn how it works, how to size it, and the mistakes that slow it down.
6 min read
· Updated
November 2026
At a glance
The definition
A put wall is a rack of cubbies, one per order. Workers scan batch-picked items and put each into its lit cubby until the order is complete.
Why it matters
Batch picking cuts travel but mixes orders together. A put wall separates them again with shelving, lights, and scanners instead of a mechanical sorter.
Where it fits
Small, multi-line ecommerce and store orders picked in batches or zones, where volume doesn't justify a unit sorter but sorting by hand on a table is too slow.
A put wall is a rack of cubbies, each assigned to one order, where workers sort batch-picked items back into individual customer orders before packing. In put-to-light setups, a light marks the right cubby after each scan, and packers pull completed orders from the other side. It does the job of a sorter with shelving, lights, and scanners.
Picking one order at a time means walking the building for two or three items. Batch picking fixes the walking: one trip, many orders. But it leaves you with totes of mixed items that someone has to separate back into orders, and that is where many batch-picking programs stall. Tables pile up with product, items go to the wrong order, and packers wait for the last piece.
A put wall is a widespread way to do that separation without a mechanical sorter. This guide covers how put walls work, why order consolidation is needed, design choices, how a put wall compares with other options, and the mistakes that slow it down. For the picking side, see batch picking; for the light hardware, see pick to light.
How a put wall works
Researchers who studied the setup describe it as widespread among online retailers. A batch of orders, picked under a batching or zoning strategy, arrives at the wall in bins. A worker takes items from each bin and, guided by put-to-light, places them into the shelf assigned to each order. The wall itself is a simple reach-through rack, and packers on the other side empty completed shelves and pack the orders.
A light-directed put wall runs a scan-and-light loop. The worker scans an item, the system finds an open order that still needs it, and a light on that cubby turns on. The worker puts the item and presses the light or scans the cubby to confirm. When an order's last item lands, a light on the pack side tells a packer the order is complete.
Why order consolidation is needed
Order picking is labor-intensive, and two common ways to cut picker travel, batching and zoning, both create a consolidation step. After batching, someone has to split the batch back into orders. With zoning, each order is split across zones and has to be brought back together before shipment.
Ecommerce makes the problem bigger. Online orders often consist of just a few order lines with low order quantities, so picking them one at a time wastes travel.
Put walls show up wherever one order's items arrive from more than one place:
Batch picking. Pickers collect items for many orders at once, and the wall separates them.
Zone picking. Orders picked in parallel across zones meet at the wall. See zone picking.
Store replenishment. Items picked in bulk are put to cubbies by store instead of by customer order.
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Put wall design choices
Cubby count and size. The number of cubbies caps how many orders can be open at once, and cubby size caps which orders fit. Size both from your actual order profile, not an average.
Reach-through or single-sided. A reach-through wall separates the put side from the pack side, so putters and packers work in parallel without crossing paths.
Light-directed or scan-only. Lights cut search time and mis-puts at the cost of hardware and wiring; the pick to light guide covers the options.
Static, mobile, or automated. Fixed walls are cheapest. Mobile walls on wheels can move to where they're needed. At higher volumes, automated put walls and unit sorters do the put mechanically; see robotic sortation systems.
Location. Put the wall next to packing so completed orders move a few feet, not across the building. See packing station design.
Size the wall to the batch. An illustrative example: if you release batches of 40 orders and most orders don't complete until near the end of the batch, a 40-cubby wall sits full while packers wait for the last items. A wall with room for about two batches lets the next batch start while packers clear the previous one. Test this with your own order data before you buy hardware.
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Put wall vs other ways to consolidate
Sort on a table or cart. No equipment, but slow and error-prone once batches get large.
Sort while picking. Pickers put items straight into order totes on a multi-order cart. This removes the separate sort step but only works when each order stays with one picker, and the cart's slots cap the batch size.
Put wall. Low capital, flexible, and easy to scale by adding walls or people. Throughput depends on labor.
Unit sorter or automated put wall. Higher throughput with fewer people, but more capital and floor space, and limits on item size and packaging. See high-mix product sorting.
Goods-to-person stations. Consolidation happens at the station as storage totes arrive. See goods-to-person picking.
Common put wall mistakes
Orders that never finish. One short pick or late replenishment holds a cubby open. Set a rule for how long an incomplete order can wait before it is pulled and handled separately.
Packers starved or flooded. The order in which bins reach the wall decides how quickly orders complete, and research on put walls focuses on sequencing bins so packers don't sit idle. A warehouse execution system can also slow order release when the wall backs up.
Mis-puts. Confirm every put with a scan or button, and check cubby contents at pack.
Items that don't fit. Route oversized or fragile items around the wall instead of forcing them into cubbies.
Poor ergonomics. Keep the busiest cubbies between knee and shoulder height and limit reaching into the top and bottom rows.
Using the wall as storage. Orders parked on the wall for hours shrink its capacity for live batches.
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Where Avatar fits
Batch picking and sorting at the wall are both item-handling work, and picking and sorting are among the tasks Avatar's robots perform. They work in existing racks, shelving, and bins, so they are worth evaluating for the pick and sort steps around a put wall you already have. At very high, steady volumes, a dedicated unit sorter may be the better fit. On Robots-as-a-Service, Avatar brings the hardware and you pay for output; see where Avatar works on the Avatar solutions page.
How It Works
The put wall process in four steps.
1
Batch pick the orders
The WMS or WES groups orders into a batch, and pickers collect every item for the batch in one trip, into totes or carts, then deliver them to the wall.
2
Scan each item
At the wall, a worker scans an item from the tote. The system matches it to an open order that still needs it and lights that order's cubby.
3
Put and confirm
The worker places the item in the lit cubby and confirms with a button press or scan, then repeats until the tote is empty and the batch is sorted.
4
Pack completed orders
When an order's last item lands, a light on the pack side signals it is complete, and a packer pulls the items, packs the order, and sends it to shipping.
Frequently Asked Questions
What is a put wall in a warehouse?
A put wall is a shelving unit divided into cubbies, each assigned to one order. Workers scan items from batch-picked totes and place each into the cubby for its order, often guided by lights. Packers then pull completed orders from the other side.
What is the difference between put to light and pick to light?
Pick to light uses lights on storage locations to show a picker which item to take and how many. Put to light uses lights on order locations, such as cubbies in a put wall, to show where to place an item. Many operations use both.
What is order consolidation in a warehouse?
Order consolidation is the step that brings all the items for one order together after they were picked separately, for example in a batch or in different zones. It can happen on a table, on a multi-order cart, at a put wall, or in an automated sorter.
When should you use a put wall instead of a sorter?
A put wall makes sense when volume is moderate or seasonal, the item mix varies widely, or capital and floor space are limited. Automated sorters suit high, steady volumes of items that fit their size and packaging limits. Many operations start with put walls and add sortation as volume grows.
Sources
1. Boysen, N., Stephan, K., and Weidinger, F. (2019). Manual order consolidation with put walls: the batched order bin sequencing problem. EURO Journal on Transportation and Logistics, 8(2), 169-193.
2. Boysen, N., de Koster, R., and Weidinger, F. (2019). Warehousing in the e-commerce era: A survey. European Journal of Operational Research, 277(2), 396-411.
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