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For shippers and receivers, few situations are more stressful than finding a damaged or missing container security seal when a shipment arrives at port. Cargo may have been tampered with, stolen or otherwise compromised, leading to delays, financial loss and potential disputes. Correctly sealing a shipping container is critical to maintaining security throughout its journey, protecting goods from unauthorised access and supporting regulatory compliance.
Choosing the right container seal not only safeguards cargo but also reassures customs authorities, shipping lines and freight forwarders that goods are accurately declared and have not been interfered with in transit. This guide explains how to select an appropriate seal, apply it correctly and keep records that support smooth customs clearance while reducing the risk of theft or tampering.
Containerisation transformed global shipping in the 1970s, allowing cargo to be packed into standardised units that can be stacked, transported and handled efficiently. While this boosted trade, it also introduced new challenges. Shipping lines needed to track contents, authorities required assurance that goods were safely transported and correctly declared, and customers wanted confidence their cargo would arrive intact. High-security container seals were developed to protect cargo, ensure compliance and deter theft, fraud and the transport of illegal goods.
A container security seal is a single-use device that locks container doors and provides visible evidence of tampering. Once applied, it cannot be reopened without clear signs of interference or destroyed for reuse. Each seal carries a unique serial number that should be recorded alongside shipping documents, including the Bill of Lading.
For international freight, high-security barrier seals are recommended. These are engineered to withstand the rigours of global shipping while providing strong tamper evidence. Barrier seals, including bolt seals, should be certified to ISO 17712:2013 for strength, durability and resistance to tampering.
Bolt seals are the most widely used. Each seal comprises a pin and barrel supplied as a matched, uniquely serialised pair. Best practice is for the serial number to be engraved on the pin head, so it remains visible after sealing. Markings along the pin shaft become hidden once sealed, making verification impossible and increasing tamper risk. Customisation options such as company logos, barcodes and colour coding further enhance traceability and reduce duplication risk. Other seal types, including cable and padlock seals, suit specialised cargo or situations where added flexibility or multiple openings are required.
Applying a seal correctly is essential. Engage a bolt seal by inserting the pin into the barrel until it locks with an audible click. A correctly applied seal cannot be reopened without bolt cutters, making tampering evident. Standard containers have two doors: the left closes first, the right second. The most tamper-resistant sealing point is typically at the bottom of the right-hand door, where a security cam passes through a locking keeper. If this feature is absent, seal the handle attached to the locking bar nearest the door edge on the right-hand door. Sealing handles on the left-hand door is not acceptable, as it opens first. Anti-spin designs are important; inferior seals may allow the pin to be rotated out of the barrel. Anti-spin bolt seals prevent this. While one correctly applied seal meets regulatory requirements, up to six points (one per locking rod) can be sealed for maximum tamper evidence.
Record seal application diligently. An authorised staff member should witness the sealing of a full container and record the seal number with time-stamped photographs. For LCL shipments, freight forwarders should supply images of the sealed container. These records provide valuable evidence for surveyors and insurers, demonstrating compliance and reducing dispute risk.
Shipping lines and customs authorities require at least one seal on international freight. The seal number must appear on the Bill of Lading and other documentation or delays may occur. Customs may conduct inspections, breaking the seal to verify contents. After inspection, officials will apply a replacement customs seal. Never break a customs seal without approval; penalties may apply.
On receipt, inspect the seal for tampering and confirm the serial number matches the documentation. If tampering is suspected, do not remove the seal until authorised representatives from the shipping line, freight forwarder or insurer are present. Use appropriately sized bolt cutters and wear eye protection when cutting, as significant force is required and debris can fly.
If a seal is broken or missing, photograph the container and seal area, notify the shipping line, freight forwarder and insurer immediately, and do not open the container until authorised. Continue photographing as the container is opened to support any claims. Swift action and thorough documentation are essential for good practice and any subsequent insurance or legal proceedings.
Choosing Universeal for container security seals provides peace of mind. With decades of experience, our products meet ISO 17712:2013 for tamper evidence and durability. Our bolt and cable seals are designed for the demands of global logistics, combining strength with traceability. Options for bespoke logos, serial numbers and colour coding further enhance security. Our high-security seals are trusted worldwide to deter theft and tampering, help prevent the movement of illegal cargo and support compliance with customs and shipping line requirements.
Frequently Asked Questions
How many seals should be used?
At least one seal is mandatory, but up to six points can be sealed for maximum tamper evidence.
Can bolt seals be customised?
Yes. Seals can be engraved with logos, serial numbers or barcodes, and colour coded.
What should I do if a seal is broken or missing?
Photograph the evidence, contact the shipping line, freight forwarder and insurer immediately, and do not open the container until authorised.
Do all shipping lines have the same seal requirements?
No. Policies vary between lines such as Maersk, CMA CGM and MSC. Always check with the carrier.
How should seals be removed safely?
Use suitable bolt cutters, wear eye protection and cut across the pin for safe removal.
For more information on Guide To Securely Seal Your Shipping Containers talk to Universeal (UK) Ltd