Security Seals Guide
What is a Container Seal?
Container seals, bolt seals and international transport security.
Show contents
- Key Takeaways
- Container door bar and sealing point
- Bolt seal: pin and body
- Why serial number matching matters
- Relationship with ISO 17712
- Application, inspection and removal
- Comparison of container, cable and plastic seals
- A seal alone does not secure the cargo
- Container seal security is more than the product itself
- Control points in the container sealing process
- Information to request during procurement
- Field application of a bolt seal
- A standards claim is not the same as test evidence
- Frequently Asked Questions
Direct answer
A container seal is a high-security class seal used in international transport to close container door bars, typically consisting of a metal pin (bolt) and a separate locking body. Matching the serial number exactly with shipping documents allows customs and logistics parties to verify whether the container was opened without authorization during transit.
What you will learn
Container door bars are closed with a seal that fixes the locking cams in place.
A bolt seal consists of a metal pin and a separate locking body the pin passes through.
Matching the serial number with the bill of lading and other shipping documents is a critical control step.
ISO 17712 is an international standard generally referenced for high-security container seals.
A seal does not guarantee cargo security on its own; it is one part of a broader inspection and oversight process.
Container door bar and sealing point
In standard containers, the door is closed with two or more vertical locking bars and cams that rotate to fix them in place. The seal is threaded through a hole on the bar to physically prevent the cams from rotating, so the door cannot be opened without cutting the seal.
Bolt seal: pin and body
A bolt seal consists of a metal pin inserted through the hole in the door bar and a separate body where the pin locks in place. Once the pin is fully seated in the body it cannot be pulled back; removal is only possible by cutting the pin with a dedicated bolt cutter.
This design balances the durability expected in container transport with clear tamper evidence; specific strength values vary by model and are stated in the manufacturer's technical documentation.
Why serial number matching matters
- The serial number of the applied seal is recorded on the bill of lading or shipping note.
- At the destination, this number is compared against the seal on the container to verify the match.
- A number mismatch or damage to seal integrity is logged as a suspected tampering incident during transit.
Relationship with ISO 17712
ISO 17712 is an international reference standard that defines physical strength tests and classification for high-security container seals, and it is recognized as a technical reference point in processes such as customs and C-TPAT. General information about this standard does not mean a specific product is certified; each product's ISO 17712 compliance should be verified with test reports specific to that product.
Application, inspection and removal
- 1
1. Close the door bars
Bring the locking cams fully into position and make sure the seal hole is aligned.
- 2
2. Apply the seal and record the serial number
Insert the pin through the hole and lock it; note the serial number on the bill of lading or shipping document.
- 3
3. Track against the document during transit
At transfer and customs points, verify the serial number against the document.
- 4
4. Verify integrity on arrival
Compare the seal's physical condition and serial number against the record; log any mismatch formally.
- 5
5. Remove at an authorized point
Have only authorized personnel remove the seal, using a proper bolt cutter, and retain the cut seal for the record.
Comparison of container, cable and plastic seals
| Feature | Container / bolt seal | Cable seal | Plastic seal |
|---|---|---|---|
| Typical use | International container door bars | Tankers, valves, longer closure points | Cartons, bags, meters, light logistics |
| Removal tool | Dedicated bolt cutter | Cable cutters / pliers | By hand or with scissors |
| Related standard reference | ISO 17712 (general reference, product-specific verification required) | Product-specific technical documentation | Usually no standard reference required |
| Typical verification method | Serial number + document match | Serial number + visual check | Visual check |
Container seal security is more than the product itself
A container seal is a physical control point proving which uniquely numbered seal was used to close a container door. A strong bolt seal alone, however, does not create a secure process. The seal number must be recorded correctly on shipping documents, the seal must be applied to the correct locking point, and the same number and physical integrity must be verified at destination.
In international transport, the term 'high security seal' can refer to a technical classification. Procurement should therefore not rely only on appearance or seller claims; conformity to the required standard, test documentation and product traceability should be checked together.
Control points in the container sealing process
| Stage | Control | Why it matters |
|---|---|---|
| Seal receipt | Serial range and quantity | Reduces risk of loss or duplicate use |
| After loading | Physical door inspection | The seal must be applied to a sound closure point |
| Application | Serial number and full engagement | A wrong or partially engaged seal does not create a reliable record |
| Documentation | Correct seal-number record | Links the physical seal to the transport record |
| Arrival | Number + physical integrity | Seeing the correct number alone is not sufficient |
Information to request during procurement
- Relevant security classification and test scope
- Manufacturer / supplier traceability and batch information
- Serial-number structure and duplicate prevention
- Logo, barcode or additional marking options
- Packaging format, carton quantity and preservation of serial ranges during shipment
Field application of a bolt seal
- 1
Inspect the door
Confirm there is no damage or looseness in the locking bars and seal point.
- 2
Record the seal number
Linking the number to the shipment record before application reduces errors.
- 3
Fully engage bolt and locking body
Confirm full engagement with a physical pull check.
- 4
Open under control at destination
After verifying number and integrity, remove using a suitable bolt cutter and safe working procedure.
Frequently asked questions
Is a bolt seal the same as other container seals?
A bolt seal is the most common type in the container-seal category, working with a metal pin and separate body structure. Some container applications may also use cable-type high-security seals, but the bolt seal is the most frequently chosen form.
Why does serial number matching matter so much?
The serial number ties the specific seal applied to a container to the shipping documents. A mismatch in numbers or damage to the seal at arrival raises a suspicion of tampering during transit and requires investigation.
Are Senkron's container seals ISO 17712 certified?
ISO 17712 is a general reference standard for high-security container seals; a specific product's compliance with it should be verified with test reports for that particular product. For up-to-date product and certification information, it is recommended to check the relevant product page or contact the sales team.
What should be done after a container seal is cut?
The cut seal should be kept together with its serial-number record and, if possible, a photo. This documentation can serve as evidence in customs or insurance processes in case of a later dispute.
What should be done if seal integrity appears compromised?
If there is unexpected damage to the seal, a serial-number mismatch, or an abnormal mark on the door bar, the situation should be formally recorded, photographed and reported to the relevant parties, such as the carrier, receiver and customs.
Does a container seal also protect the cargo's contents?
No. A seal makes it visible whether the door bars were opened without authorization; it does not physically protect the cargo's contents. Content security is provided by separate processes such as proper stowage, insurance, oversight and carrier selection.
Do different carriers use the same serial number format?
No, the serial number format can vary from manufacturer to manufacturer and sometimes by carrier agreement. What matters is that whichever format is used, it is consistently recorded in the shipping documents.
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