Security Seals Guide
What is a Security Seal?
Definition, function and basic use cases of security seals.
Show contents
- Key Takeaways
- Lock vs. seal: what is the difference
- Tamper-evident and single-use design
- Seal families
- Comparison of seal families
- Basic sealing steps
- The real role of a security seal in the security chain
- Basic seal classes by need
- Questions to answer before selecting a seal
- How should the seal lifecycle be managed?
- Important: a seal does not provide absolute security
- Frequently Asked Questions
Direct answer
A security seal is a single-use, tamper-evident device that, once applied to a door, cover, valve, meter or transport unit, cannot be removed without breaking or leaving visible damage. Unlike a lock, it does not physically protect the contents; its main job is to make unauthorized opening visible and to record chain-of-custody through a unique serial number.
What you will learn
A seal does not physically resist attack like a lock; it makes tampering visible instead.
It is single-use: once opened or cut, it cannot be reclosed.
The serial number links a seal to a specific shipment, vehicle or responsible party.
The main families are plastic, cable (steel-wire), container/bolt and meter seals.
Proper sealing is a discipline made up of correct product choice, serial-number logging and regular inspection.
Lock vs. seal: what is the difference
A padlock is designed to physically prevent an opening and is usually reusable. A security seal works on a different principle: deterrence and evidence. Its goal is not to make opening impossible, but to make any opening instantly and undeniably visible.
For this reason, seals are typically used together with locks as a complement, not a replacement. A seal added to a locked cabinet door, for instance, also reveals whether the lock was opened with a key and closed again.
Tamper-evident and single-use design
- Opening produces a visible break, tear or deformation at the moment of tampering.
- Reclosing or repairing it to look original is not practically possible.
- This property makes a seal a verification and evidence tool rather than a security barrier.
- Serial number, barcode or QR printing links the physical trace to a digital record.
Seal families
There are four main seal families on the market, each shaped by a different application point: plastic seals for light-to-medium volume operations, cable (steel-wire) seals for longer closure points, bolt / high-security seals for international container transport, and dedicated meter seals for small-diameter points such as meters and valves.
The choice between families depends on the diameter and length of the point being closed, the required perception of security, whether removal tools are needed, and operation volume.
Comparison of seal families
| Family | Typical use | Security perception | Removal method |
|---|---|---|---|
| Plastic seal | Cartons, bags, luggage, light logistics | Basic / visual deterrence | Break by hand or cut with scissors |
| Cable seal | Tankers, valves, equipment, longer closure points | Medium-high | Requires cable cutters / pliers |
| Container / bolt seal | International container transport | High | Requires a dedicated bolt cutter |
| Meter seal | Electricity, water and gas meters and valves | Basic-medium | Tear off by hand or cut |
Basic sealing steps
- 1
1. Choose the right seal
Select the seal family that matches the diameter, length and required security level of the point to be closed.
- 2
2. Record the serial number
Note the applied seal's serial number on the delivery note, handover form or digital record.
- 3
3. Apply correctly
Thread the seal through the closure point, making sure the locking teeth fully engage.
- 4
4. Inspect
At delivery or arrival, compare the serial number and the seal's physical condition against the record.
- 5
5. Remove properly
Remove the seal only at an authorized point, using proper tools if needed, and keep the cut seal as part of the record.
The real role of a security seal in the security chain
A security seal is not a lock that stops theft by itself. Its role in the security chain is to make unauthorized interference visible and to make it possible to investigate when and at which custody point an incident may have occurred. For that reason, recording the serial number, applying the seal through an authorized person and inspecting it at destination are as important as choosing the correct seal.
Applying a seal to a vehicle door without recording its number on the shipping document or checking it at arrival creates little operational value. Effective use comes from running the physical seal, record, responsibility and verification steps together. The seal is the visible part of the system; the actual security comes from process discipline.
The same principle applies to a small warehouse shipment and to international container transport. What changes is the seal family, required mechanical strength, recording method and inspection frequency. A plastic seal may be sufficient for a low-risk bag or crate, while bolt or cable seals that meet the relevant security requirements are evaluated for international freight containers.
Basic seal classes by need
| Need | Recommended family | Inspection method | Typical record |
|---|---|---|---|
| Bags, sacks, crates and light warehouse flow | Adjustable or fixed-length plastic seal | Visual check of body, lock point and serial number | Dispatch note, picking list or mobile record |
| Vehicles, tanker valves, IBCs and long closure points | Steel cable seal | Cable integrity, cut marks, lock body and number | Serial record matched to vehicle or shipment |
| International freight container | Appropriate bolt or high-security seal | Door handle, seal body, pin and serial number | Bill of lading, loading record and delivery inspection |
| Electricity, water, gas meters and small valves | Meter or fine-wire seal | Wire continuity, body closure and marking | Subscriber, meter or service-order record |
Questions to answer before selecting a seal
- What are the diameter, length and geometry of the closure point?
- Is the goal only to show tampering, or is high pull strength also required?
- Will the seal be removed by hand, scissors, cable cutters or a dedicated bolt cutter?
- Which markings are required: serial number, logo, barcode or QR code?
- Will the seal face outdoor exposure, temperature, chemicals or long storage periods?
- Who will inspect the seal and in which system will the serial number be stored?
How should the seal lifecycle be managed?
- 1
Purchase and receipt
The product is selected against the technical need; incoming batch, serial range, print quality and packaging integrity are checked.
- 2
Secure storage
Unused seals are stored in a controlled area and access by unauthorized people is restricted.
- 3
Issue and record
The seal number is linked to a shipment, vehicle, meter, employee or work order.
- 4
Application and pull check
The seal is routed through the correct point, fully locked and verified with a light pull test.
- 5
Delivery and exception handling
At arrival, the number and physical condition are compared; if there is a mismatch, break or suspicious mark, opening is paused and the exception is documented.
Frequently asked questions
Does a seal replace a lock?
No, a seal does not replace a lock; it complements it. A lock makes physical opening harder, while a seal makes any opening visible and records it.
Can a seal be reused once opened?
No. Security seals are designed for single use; once opened or cut, they leave a break, deformation or tear and cannot be closed again to look original.
Why does the serial number matter?
The serial number links a seal to a specific shipment, vehicle, date and responsible person. This link allows the correct seal to be verified as still intact at the delivery point.
Which seal family should be chosen for which case?
As a general rule, plastic seals suit small, low-volume points; cable seals suit longer or more demanding closure points; bolt / high-security seals suit international container transport; and dedicated meter seals suit thin points like meters.
What should be done after a seal is cut?
The cut seal should be kept for a defined period, or photographed, together with its serial-number record. This helps prove which seal was applied at which point in case of a later dispute.
Does a seal prevent all forms of theft?
No. A seal is a verification tool that makes unauthorized opening visible; it does not guarantee stopping a determined, tool-equipped intrusion on its own. Real security comes from combining seals with proper locks, oversight and process controls as a whole.
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