Do Not Stack Symbol: Meaning, Standards, and Freight Impact

The do not stack symbol is the standardized packaging mark, listed as symbol No. 15 in ISO 780, that tells anyone handling a shipment to place no load on top of the package.¹ It protects cargo whose packaging cannot safely bear compression from freight stacked above, and applying it correctly matters for both cargo protection and any damage claim that follows mishandling.

What the Symbol Means

The graphic shows two boxes stacked vertically with a bold diagonal line or large X drawn through the arrangement. The top box represents cargo that should not be placed there, and the strike-through makes the prohibition unmistakable even without text. Because it relies on a visual concept rather than words, the same mark carries the same instruction to a dock worker in Memphis, a forklift operator in Hamburg, or a warehouse crew in Shanghai.

ISO 780 defines its meaning as: stacking of the package is not allowed and no load should be placed on it.¹ That goes beyond prohibiting another pallet on top. Even a single loose box placed on a marked package violates the instruction.

Size, Color, and Placement Rules

ISO 780 and its U.S. counterpart, ASTM D5445, both specify three standard symbol heights: 100 millimeters, 150 millimeters, and 200 millimeters. Larger or smaller versions are allowed when the package size makes them necessary, provided the proportions stay consistent.¹² The 100mm size works for standard corrugated boxes. The 200mm size suits large crates or palletized loads that handlers view from several feet away.

Symbols must be printed in black. Where the package surface is too dark for black to show clearly, a contrasting background panel goes behind the symbol, preferably white.¹ Warehouse lighting is often poor and box surfaces get dusty. A faded or camouflaged symbol is nearly as useless as no symbol at all.

Standard practice is to print the mark on at least two sides of the package so it stays visible regardless of how the box is oriented in a trailer or on a rack. For palletized loads, position the symbols where they remain visible after the unit is formed, since shrink wrap or adjacent freight can obscure marks placed too low.

The Standards Behind the Mark

ISO 780 is the global framework for pictorial handling marks. It exists because written instructions in the shipper’s language are worthless once freight crosses a border or reaches handlers who speak a different language. The standard itself notes that pictorial symbols offer the best possibility of conveying the shipper’s intention and reduce loss from incorrect handling.¹

ASTM D5445 plays the same role domestically. It establishes the same core set of symbols for marking packages to indicate special handling and storage needs.³ The two standards align closely on symbol design, sizing, and color, so a package marked to ISO 780 specs will also satisfy most domestic handling requirements.

Related Handling Symbols

The do not stack mark rarely appears alone. Several companion symbols from ISO 780 frequently show up on the same package, especially when the contents are fragile or orientation-sensitive:

Fragile, shown as a wine glass, means contents break easily and require careful handling throughout transit.
This Way Up, shown as two upward arrows, means the package has a single correct orientation and should not be flipped or tilted.
Keep Dry, an umbrella with rain, means moisture will damage the contents.
Temperature Limitations, a thermometer with a range, means store and transport within a specified temperature window.
Stacking Limitation, a number on stacked boxes, means the package can support stacking, but only up to a specified number of units.

Stacking limitation is worth distinguishing from do not stack. Stacking limitation means you can stack, but only this many high. Do not stack means no weight on top, period. Confusing the two produces exactly the damage both marks are designed to prevent.

Physical Deterrents That Reinforce the Mark

A printed symbol works only if handlers notice it and comply. For high-value or especially fragile freight, shippers add physical devices that make stacking difficult or leave evidence of mishandling when someone tries.

Do-not-stack cones are inexpensive cardboard pyramids that strap or tape onto the top of a pallet. They project above the load, creating an obvious physical barrier. A crushed cone also doubles as proof that someone ignored the restriction, which strengthens insurance claims later.

Vertical strapping that passes through the pallet void and over the top of the load ties cargo firmly to the pallet base and gives the shipment a rigid profile that discourages casual stacking. Horizontal strapping stabilizes individual layers within the load. Combining strapping with stretch wrap is standard for shipments that need both rigidity and surface protection. Corner boards and edge protectors reinforce the package against compression and also signal to handlers that the shipper invested in protection.

How the Mark Affects Freight Costs

Marking a shipment non-stackable has real financial consequences beyond the cost of labels and cones. Under the National Motor Freight Classification system, freight class is determined by density, and density is calculated using the shipment’s extreme outer dimensions, including any do-not-stack cones or caps sitting on top.⁴ Those cones add height without adding weight, which lowers the density calculation and pushes the shipment into a higher freight class with steeper rates.

LTL carriers also commonly apply accessorial fees for non-stackable freight, including floor-loading charges, exclusive-use trailer fees, and special handling surcharges. The cost gap between stackable and non-stackable shipments can be significant. Some shippers invest in stronger packaging that can handle stacking loads rather than paying the ongoing premium for non-stackable classification. Running the numbers on that tradeoff is worthwhile before defaulting to a do-not-stack label.

Warehouse Safety Rules Reinforce the Instruction

The symbol also intersects with workplace safety law. OSHA’s materials handling regulation requires that materials stored in tiers be stacked, interlocked, and limited in height so they remain stable and secure against sliding or collapse, and explicitly states that storage must not create a hazard.⁵ Placing freight on top of a package marked do not stack creates precisely the instability that rule targets. A collapsed stack that injures a worker can trigger OSHA citations on top of any cargo damage liability.

Why the Symbol Matters in a Damage Claim

When a carrier stacks freight on a package clearly marked do not stack and the goods arrive damaged, federal law heavily favors the shipper. The Carmack Amendment, codified at 49 U.S.C. § 14706, imposes strict liability on motor carriers for cargo damage in interstate commerce.⁶ The shipper does not need to prove the carrier was negligent or identify exactly where in the journey the damage occurred.⁷

Instead, the shipper shows three things: the goods were delivered to the carrier in good condition, they arrived damaged, and the shipper suffered a specific dollar loss. The burden then shifts to the carrier to prove itself not at fault by invoking a recognized defense such as an act of God, a public enemy, or the shipper’s own fault.⁷ The do not stack symbol becomes powerful evidence in this framework. A carrier trying to blame the shipper for inadequate packaging will struggle when the package carried clear handling instructions the carrier ignored. A shipper who fails to mark fragile or non-stackable goods gives the carrier ammunition to argue the damage resulted from insufficient labeling.

Documenting the Mark for Your Records

Record the handling instruction on the bill of lading. The bill of lading is the contract between shipper and carrier, and handling requirements noted on it become part of that agreement. A carrier who signs for a shipment described as non-stackable has acknowledged the restriction in writing.⁶

Photograph the package before it leaves your facility. Capture the do not stack symbol, the overall condition of the packaging, and any physical deterrents like cones or corner boards. Time-stamped photos establish that the goods left your hands in good condition, which is the first element you need under the Carmack Amendment. For high-value loads, electronic shock and tilt recorders capture real-time data on impacts, orientation changes, and location throughout transit, which can pinpoint when and where mishandling occurred.

Inspect every shipment on arrival and note damage on the delivery receipt before signing. Carriers routinely use a clean signature to argue goods arrived intact. File written claims promptly after discovering damage; federal law sets deadlines for both the initial claim and any subsequent lawsuit, and missing them can forfeit your right to recover.

1
International Organization for Standardization. ISO 780-1997 – Packaging — Pictorial Marking for Handling of Goods
2
ASTM International. ASTM D5445-11a – Standard Practice for Pictorial Markings for Handling of Goods
3
ASTM International. ASTM D5445-21 – Standard Practice for Pictorial Markings for Handling of Goods
4
National Motor Freight Traffic Association. Packaging and Class – How Packaging Decisions Change Density and Your Invoice
5
Occupational Safety and Health Administration. Handling Materials – General
6
Office of the Law Revision Counsel. 49 U.S. Code 14706 – Liability of Carriers Under Receipts and Bills of Lading
7
U.S. Department of Transportation. Cargo Liability Study