Technical Foundation
What Is a Security Seal?
A security seal is a single-use, tamper-evident device that secures a container, trailer door, valve or enclosure such that any attempt to open it without breaking the seal is visually obvious, and each seal carries a unique serial number for chain-of-custody tracking. Seals are classified under ISO 17712 into three security levels — Indicative (visual evidence of tampering only, no significant resistance to force), Security (resists a defined level of tool attack), and High Security (bolt and cable seals meeting the highest force-resistance and tamper-evidence testing, required for most international container shipping).
Seal type is matched to the closure being secured: bolt seals thread through container door locking bars and are cut with bolt cutters, providing high strength for high-value or regulated cargo; cable seals wrap through smaller openings like valve handles or hasps where a rigid bolt seal wouldn't fit; plastic indicative seals are low-cost, numbered zip-tie-style seals for lower-risk applications like utility meters or internal quality checks where tamper evidence matters more than physical resistance.
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| Spec | What It Means | Why It Matters |
|---|---|---|
| ISO 17712 Classification | Indicative, Security, or High Security | High Security required for most international ocean/customs container shipments; Indicative sufficient for lower-risk internal use |
| Seal Type | Bolt, cable, plastic strip, metal strap, padlock | Matched to the physical closure — bolt for container locking bars, cable for valves/hasps, plastic for light-duty applications |
| Serial Numbering | Sequential unique numbers, often with barcode | Enables chain-of-custody verification and audit trail from origin to destination |
| Material | Steel (bolt/cable), ABS/polypropylene (plastic) | Determines resistance to cutting tools and environmental durability during transit |
| Customization | Custom printing, company logo, color coding | Used for brand verification and quick visual identification of authorized seals vs. counterfeits |
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Applications
Where Security Seals Get Used
Security seals are specified anywhere a closure needs tamper-evident, serialized verification for chain-of-custody or regulatory compliance.
International Shipping & Freight
ISO 17712 High Security bolt seals required on ocean container shipments crossing international borders and customs.
Tanker & Bulk Liquid Transport
Cable seals used on tanker truck valves and manway covers to verify contents haven't been accessed in transit.
Trucking & Logistics
Bolt and cable seals used on trailer doors to provide tamper evidence and chain-of-custody documentation.
Utility Meter Security
Plastic indicative seals used on electric, gas and water meters to detect unauthorized tampering.
Pharmaceutical & High-Value Cargo
High security seals combined with serialized tracking to meet regulatory chain-of-custody requirements.
Warehouse & Inventory Control
Numbered plastic seals used on internal totes and cages to verify contents haven't been accessed between counts.
FAQ
Security Seals Questions, Answered
What does ISO 17712 classification mean for security seals?
ISO 17712 defines three seal classes based on standardized testing: Indicative seals only provide visual evidence that tampering occurred, with minimal resistance to cutting; Security seals resist a moderate, defined level of tool attack; High Security seals (bolt and cable types) must pass the most rigorous force-resistance testing. Most international ocean freight and customs regulations require High Security seals on shipping containers.
What's the difference between a bolt seal and a cable seal?
A bolt seal is a rigid metal pin that locks into a body and threads through a container's door locking bars, offering high resistance to cutting and bending — the standard for container shipping. A cable seal uses a flexible steel cable instead of a rigid bolt, allowing it to pass through smaller or irregularly shaped openings like valve handles, padlock hasps or tanker manways where a rigid bolt seal wouldn't fit.
Do plastic seals provide real security or just tamper evidence?
Plastic indicative seals provide almost no resistance to cutting — a pair of scissors defeats most of them in seconds — so their value is purely in tamper evidence and chain-of-custody documentation via the unique serial number, not physical security. They're appropriate for lower-risk internal applications like utility meters or inventory control, not for high-value or regulated international cargo.
Why do security seals need unique serial numbers?
The serial number creates a documented chain of custody — the number applied at origin is recorded on the shipping manifest, and the receiving party verifies the same number is intact upon arrival, immediately flagging if a seal was cut and replaced with a different one in transit. Without serialization, a broken seal could be silently swapped for an intact-looking substitute.
Can security seals be reused?
No — security seals are designed as single-use devices specifically because reusability would defeat their tamper-evidence purpose. Once a seal is cut or broken to open the container or valve, it must be discarded and a new, uniquely numbered seal applied and documented for the next closure.
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