Item Properties
Every item in LOP carries a set of properties that control how the optimizer places it and how the constraint engine validates the resulting load plan. Understanding what each property does helps you build more accurate load plans and avoid unexpected results.
Weight
Field: Weight (kg or lbs, depending on your unit preference)
Weight is one of the most consequential item properties. It is used in three distinct ways:
Payload enforcement — The sum of all item weights in a container must not exceed the container's maximum payload. If the total weight exceeds the limit, the optimizer will attempt to distribute cargo across additional containers.
Center of gravity calculation — The optimizer calculates the weighted centroid of all placed items to determine whether the load is balanced. Heavier items placed too far to one side will degrade the Weight Balance score and may trigger a balance warning.
Stacking safety — When one item sits on top of another, the optimizer checks the cumulative weight bearing down against the lower item's crush strength. If the weight exceeds the crush limit, the placement is rejected.
Always enter the weight of one unit of the item as it will be loaded — including all packaging, pallets, and internal contents. A weight of zero is technically valid but will cause the optimizer to ignore this item's contribution to the center of gravity calculation, which can result in misleading balance scores.
Fragile
Field: Fragile (toggle)
When an item is marked fragile, the optimizer enforces a hard constraint: no other item may be placed on top of it. This applies regardless of the stacking or weight settings of the item above.
Fragile items are visually distinguished in the 3D viewport to make the load plan easy to review.
Use this setting for:
- Glass, ceramics, or delicate electronics
- Items in thin-walled packaging that cannot bear any load
- Any cargo where stacking from above would risk damage
Stackable
Field: Stackable (toggle)
Stackable controls whether other items are permitted to rest on top of this item. When stackable is turned off, no items will be placed above this one.
The distinction between Fragile and Stackable is intentional:
| Can have items placed on top? | Can be placed on top of other items? | |
|---|---|---|
| Fragile = true | No | Yes |
| Stackable = false | No | Yes |
| Both | No | Yes |
In practice, most items are stackable. Turn stackable off for items that cannot structurally support weight from above — for example, a hollow plastic container or an irregularly shaped item that would create an unstable base.
Setting Stackable to false is a hard constraint. The optimizer will never place any item on top of a non-stackable item — this is enforced strictly during both initial placement and optimization refinement. You do not need to also set Max Weight on Top to 0.
Max Weight on Top
Field: Max Weight on Top (kg or lbs, or leave blank for unlimited)
This is a hard crush-strength limit. It defines the maximum cumulative weight that may be placed on top of this item. The optimizer treats this as an inviolable constraint — any placement that would cause the weight on top to exceed this value will be rejected.
Leave this field blank (or set it to null) to indicate that this item has no crush-strength limit.
Practical guidance:
- A standard wooden pallet can typically support 1,000–2,000 kg on top
- A corrugated cardboard carton of average quality supports roughly 100–300 kg depending on stacking pattern
- Drums of hazardous liquids typically have manufacturer-specified stack limits — use those values directly
Orientation
Field: Orientation (dropdown)
Orientation controls which rotations the optimizer is permitted to apply to this item when searching for a placement. LOP supports six cuboid rotations (all 90-degree combinations of length, width, and height axes).
| Setting | Meaning |
|---|---|
| Auto | The optimizer freely chooses the best rotation from all permitted rotations. Maximizes packing density. |
| This Side Up | The item must remain upright — height axis stays vertical. The item can be rotated in the horizontal plane (4 rotations), but cannot be tipped on its side. |
| Vertical Only | The longest dimension must be vertical. Use for tall, narrow items such as rolled textiles or standing pipes. |
| Horizontal Only | The longest dimension must be horizontal. Use for items that must lie flat, such as flat-pack furniture or sheet glass. |
Overly restrictive orientation settings reduce the optimizer's ability to find efficient packings. Use This Side Up when physically required (liquids, fragile surfaces, printed labels that must be readable) rather than as a general precaution. For most solid cargo, Auto will produce the best results.
SKU
Field: SKU (optional text)
A stock-keeping unit identifier. This field is purely informational — the optimizer does not use it. The SKU is stored with the item and included in all CSV and Excel exports, making it easier to cross-reference the load plan with your warehouse management system.
Notes
Field: Notes (optional text)
A free-text field for any additional handling instructions or contextual information about the item. Notes appear in exported load plan reports and PDF documents.
Examples of useful notes:
- "Keep dry — do not stack on floor without pallet"
- "Lithium battery — see IATA Section II declaration attached"
- "Customer priority — load last for first delivery"
Separation Tags
Field: Separation Tags (multi-select)
Separation tags enforce minimum physical distances between incompatible cargo types. This is primarily used for hazardous materials compliance and food safety segregation.
When two items in the same container have incompatible tags, the optimizer calculates the center-to-center distance between their placements and checks it against the required separation distance. If the constraint cannot be satisfied, one of the items is marked as unplaced.
Built-in separation rules:
| Tag Combination | Minimum Distance |
|---|---|
hazmat_class_1 ↔ hazmat_class_2 | 3 meters |
Any hazmat ↔ food | 5 meters |
wet ↔ food | 3 meters |
Separation constraints are hard constraints — they cannot be relaxed by the optimizer. If your container is too small to satisfy all separation requirements simultaneously, some items will be left unplaced. In that case, consider using multiple containers and assigning incompatible cargo to separate containers entirely.
You can assign multiple tags to a single item. For example, a drum of industrial cleaning fluid might carry both hazmat_class_3 and wet.
Library Sync
When you use items from the Item Library, LOP tracks whether the library version has changed since the item was added to your plan. If you update an item's properties in the library (for example, changing its weight or stackable setting), plans using that item will show an amber "⚠ Updated" badge next to the item name.
Click the badge to sync the latest properties from the library into your plan. This updates dimensions, weight, stackable, fragile, max weight on top, orientation, and notes.
Library sync is one-directional: library → plan. Editing an item's properties within a plan does not change the library version. If you want your changes to apply to future plans as well, update the item in the Item Library directly.
Setting Properties via Import
You can set Stackable, Fragile, and Max Weight on Top directly from your Excel or CSV file during import. Include columns with these names in your spreadsheet — LOP recognizes them automatically.
- Stackable and Fragile accept:
1/0,yes/no,true/false - Max Weight on Top accepts a numeric value in kg or lbs
See Importing from Excel or CSV and AI Smart Detection for more details.
Group ID
Field: Group ID (optional text)
Group ID is used to keep related items physically close to each other in the loading plan. Items sharing the same Group ID will be placed near each other whenever the optimizer can do so without significantly reducing overall utilization.
This is a soft constraint — the optimizer will try to honor grouping, but will not sacrifice a significantly better overall placement to enforce it. See Quantity & Groups for more detail and best practices.