Field note ·
Why fast lines still end up on the top beam
ABC by units shipped is not the same as ABC by cube. Pick faces fill from the easy beam first, then the awkward remainder is left for the lines that actually move.
ABC rankings that sort only by units shipped will put a fast, tiny bottle next to a fast, awkward case. The bottle belongs where a picker can reach without a step-stool. The case belongs where a pallet jack can square up. Height is a slotting decision, not leftover space.
On a recent ambient site the top beam of the forward pick was almost entirely A-lines by unit count. Nobody had plotted cube. The lines that actually filled a tote in two picks sat at ankle height because they were bulky and had been received during a wet week when the easy beams were already full. Velocity in units had won the argument in a spreadsheet; cube had won it on the floor, in the wrong direction.
We group lines twice: once by units over a representative stretch, once by cube where the extract allows it. Where cube is missing, we sample case sizes on the beam rather than invent weights. The golden zone — roughly knuckle to shoulder for the people who pick that aisle — is reserved for lines that are both frequent and comfortable to handle. Fast and heavy still needs a low beam; fast and light can share height with slower neighbours if the pick path does not double back.
Replenishment changes the picture. A high beam that looks perfect for a slow reserve pallet becomes a problem if that pallet feeds a golden-zone pick face every hour. Then the “slow” location is in the travel path of the people you were trying to protect. Slotting height and replenishment frequency have to be drawn on the same map, or the map is a wish.
If your A-lines live on the top beam, walk the aisle at pick hours before you reprint labels. Count how often a picker waits for a truck. That wait is often the true cost of treating height as leftover space.