Guide to Tamper Evident Security Seals

(About Seals, Seal Selection, and Use)

Selecting the Right Seal

Six Key Decisions

  • Choose a seal type that physically fits the device or fixture to be sealed
    Look carefully at lengths, diameters, and available space to lock and inspect the seal. Also consider the environment and duration of use.

  • Use seals with an appropriate level of strength
    Consider what strength will not accidentally break, and what how strong it should be for cutting or removing. Also, does the seal deter unauthorized opening to the extent called for?  Match costs relative to the risks of loss from violated seals.  Usually the stronger the seal the higher the cost. 

  • Use a manageable closing system
    The closure method of your seals should match the capability of the facility and people applying and inspecting the seals.  If special tools are required to close or to read a seal, consider both cost and availability of the tools.  Complex systems without adequate equipment and trained staff are not effective. 

  • Materials should be suitable for the conditions where the seals are to be used.
    Consider climate, corrosion, physical stresses, duration of use, plus handling and storage conditions.  We offer a variety of plastics and metals in a wide range of strength categories.

  • Make sure the seal has capacity to contain all of the information needed
    Information may include as little as a serial number or a few letters.  Or you may need a lot.  Seals can show information like logotypes, product codes, bar codes, source plus destination indicators, and load or content data.


Make American Casting & Mfg. your seal supplier/partner.

We have the knowledge, experience, credentials and skills you need. AC&M will work with you as a partner in developing a comprehensive program including best practices for optimizing the way you obtain, deploy, and monitor your seals.

  • AC&M has over a century of reliable service, highest quality, industry credentials and sealing experience.

  • Our US headquarters holds control of raw material, production, warehousing, delivery, and customer service in a single location. Advanced production integrated with personal attention to each order makes possible the most rapid and efficient service available and allows us to meet the unique and varied needs or our customers.

  • We offer customized markings, colors, packaging, delivery schedules and much more – plus a fast ship program for stock seals that only requires a phone call, email, or online purchase, to get same day or next day shipment.


Know the Purpose

Tamper Evident SealSecurity seals are a tool to deter and detect unauthorized opening of a closure. They differ from locks in that they are intended to be used only once, and then destroyed.

When seals are found tampered or violated it is the tampering indicators that allow the user to begin investigating any issues, ultimately catching, and stopping the violator.

Seals alone do not stop entry. But a higher strength seal can slow a thief and reduces the likelihood of vandalism or theft of “convenience” by someone with no concern for leaving evidence.

Seal violation takes various forms including hiding the opening and closing to fool the untrained observer, substitution of parts, modification of markings, or substitution of whole (clone) seals. An initial discovery of tampering may occur when the seal is cut and taken out of use. It may also be found on site by scheduled inspection, or on examination of the seal after it is opened by the user and checked at another location. If a seal is never examined by an informed person, tampering or violation of the seal may not be discovered at all.

Once discovered, the process is normally to systematically narrow the time and/or place the violation occurs. This may take several cycles of use, but can tell an investigator who potentially is violating (or attempting to violate) a secured container or device, when it happened, as well as where it happened (if it is a moving application like rail or truck)

Stronger seals require stronger tools and more time to remove. However, for investigative and enforcement purposes they serve the same function as lighter seals. With systematic inspection and observation all seals can help catch or deter unauthorized opening.


(Seals vs Locks)

Since the 1980 seals which function both as a strong disposable lock and a disposable seal entered the market. First bolt type seals, and then cable seals. Primarily they were introduced for rail cars, trucks, and intermodal containers.

Keyed locks have disadvantages in many transport systems because they are not controlled by one company or agency. They are not readily returned for re-use except in a highly closed and regulated operation. The potential for undetected losses is higher with locks left unattended, and the cost per unit is high. Bolt and cable seals are as strong as many locks and are used once and done, at lower cost overall. It is much easier to control and monitor a seal, and it provides useful functions for keeping information related to assets or goods in transit.

In stationary uses like gates, doors, and other access points, locks still can be of use but only if there is a very good control and inspection system along with close monitoring of keys.


Seal Classifications Under ISO-17712:2013

The 3 seal categories under ISO-17712-2013 are:



Indicative (I) seals

Indicative seals are the most commonly used type and are found in countless applications. They serve the function of providing tamper evidence, but are easily broken or cut open with common tools or sometimes by hand. They are often called tamper-evident seals or tamper seals, although every security seal we offer provides tamper evidence.

These include almost any closure, like totes, drums bags, wheel carts, ballot boxes, control levers, valves, money bags, and more. Many trucks are secured with indicative seals. Also, stationary closures such as utility meters, cabinets, lockers, storage bins, and cages.

Also included in the indicative seal category are adhesive tamper evident labels and tapes which have a similarly long list of uses.


Security (S) Seals

These are of intermediate strength and require a stronger or larger tool (and more effort) to cut open than do indicative seals. Added strength helps avoid accidental breaking in rough applications, or easy entry without tools. The most popular among these are cable seals which are found on many of the same applications as indicative seals. They are used on higher value or higher risk functions such as fuel tankers, hazmat, high value utility meters, and sensitive entry or access points. Processing valves and controls for chemicals and other highly sensitive industries are users of this seal type.

Security seals exceed the strength of indicative seals but do not meet strength test standards of the 3rd category -- “High Security”.

Security Seals


High Security (H) Seals

High security seals are tested and certified to meet the standards of ISO-17712:2013 for specific strengths. They can provide tamper-evidence and also serve as a one-time lock to slow down and deter theft or vandalism, and they require large tools to cut open.

The standard testing for this category specifies minimum resistance to specific levels of pull, bending and crushing. All certified High Security seals are stamped with the letter (H) and the identity of the manufacturer. Most common uses are for international shipment via ocean containers, or doors on rail cars and long-haul trucks. AC&M offers a range of (H) certified seals of both bolt type and cable type. All seals with the “H” certification must have a test certificate from an independent ISO approved facility. AC&M can provide that certificate for our High Security Seals.

Additionally, Conformance and independent auditing under Annex A of the ISO standard provides assurance that a manufacturer follows accepted practices required for compliance.
(See the addendum to this guide regarding conformance to ISO standards for seals.)

This is to assure the manufacture keeps proper control and documentation of its seals and marking to assure the end user they are getting uniquely marked seals that are from the original source, that can be traced from production to delivery.

Refer to the web site of ISO-17712: 2013 for more on this topic.
Included in the ISO seals program are standards for electronic seals (E-Seals). Some are already deployed and in limited use, mostly on ocean shipping containers of sensitive cargo. Their value is being assessed.

High Security Seals



Indicative & Barrier Seals

The 3 classifications above of ISO-17712 only verify that seals meet tests for strength in a laboratory. A seal tested to standards for the first 2 groups (“Indicative” and “Security”) don’t need certification for practical reasons, because it simply confirms they do not meet the strength tests of the “High Security “H” category. It tells you nothing more.

Strength does not equal security. The term High Security can mislead a buyer about the real level of security they are getting in their application. Much depends on the seal design, how it fits the application and especially on how, and how well, the seals are applied, controlled and examined. Even a strong or well-made High Security Seal has little security value if not used and monitored properly.

We group seals first as either INDICATIVE SEALS or BARRIER SEALS.

This separates seals easily broken or cut with household shears (indicative) from much stronger seals that require stronger cutting tools to open (barrier).

A good barrier seal that may not be certified under ISO as “High Security” may be a better seal for your purposes. Many uses of stronger seals do not need formal certification. They do call for a quality barrier seal.

We offer all options, giving our customers have practical choices.

NOTE: Most refer to any tamper evident seals a “Security Seal”, regardless of category. It is a generic term and separates tamper evident seals from seals used for purposes not related to security. (ie o-ring seals, gaskets, weather seals and the like)



With today’s concerns for potential terrorist acts, seals have become an import part of the effort, as a tool to monitor goods in transit and storage. Especially watched are international container shipments. The challenge of immediacy in anti-terrorism requires a much higher degree of knowledge, control, and attention to the seal throughout its use.

Under ISO and other organizations, standards for the production and practices in supply of security seals are regularly updated. (See “Various Security Groups and Standards.)


Do Seals Really Help?

Seals by themselves cannot protect cargo containers or any other closures from access by motivated people who intend harm or theft. Nor can any technology. It is unrealistic to expect absolutes. But seals are an important tool in security programs.

Each step toward improving design and application of seals and related technologies improves the odds of detecting and preventing loss and reduces points of opportunity. Detection is what security measures are intended to accomplish.

We supply seals and other devices to almost every segment and enterprise of industry, government, and the military. While each situation is unique, there is one over-arching and often misunderstood reality of the effectiveness of security seals.

All Security Seals can be defeated.
and All Security Seals can be effective.

Both statements are true, and the paradox is explained this way:

  • Seals can be defeated or bypassed - without leaving obvious evidence; given sufficient opportunity, time, and tools. So can safes, door locks, padlocks, alarms etc.

  • Seals can be made to work effectively in tamper detection, with proper application, a strong and well-enforced program for control and inspection, plus use of well-considered and adaptable countermeasures.


Making Your Seals Work Effectively

In order for a seal to be effective there must be a reasonable
level of reliability at the point of locking, and upon opening.

Who is handling the seals (and how) matters most? Seals are used to great benefit in countless applications every day. There are sometimes questions or debates about which type of seal works best. But, if you use seals, it is more important to deal with how they will be handled first. Deciding your approach and steps to sealing will help decide the type of seal that fits your purpose.

For a seal to be effective there needs to be a real effort on the user’s part. Using seals effectively is a far greater challenge than finding a design that fits.

Theft, smuggling, sabotage, and other nefarious activities are human behavior issues. They should be met by flexible methods, and people who are as creative, determined and as skilled as the criminals who carry out such acts. Relying too much on technology without addressing the human factors will not get the job done.

ie. To repeat the statement above in other term: You need people who are trained and trusted handling your seals.


Tips, Countermeasures, and Strategies

There are many techniques or “tricks” which will help to make a seal more effective. All must be backed by real consequences and personal responsibility.

It is important that seal users are regularly evaluating and improving their own measures that will best enhance the seals’ worth. Outlined below are some suggested steps that can be taken to make seals useful and effective. These are just some of the techniques in summary form which are worth considering. (Also see “Best Practices” following this document.)

  • Layered Technology
    • Combining Devices, Seal plus tape, or multiple matching labels, or multiple seals
    • Enhanced Visual ID, - adding unique mark or indicators at time of locking
    • Segregated sealing (seal separate from bar code, RFID tag or other identifiers)

  • Variations Within Standard Seals
    • Colors and alpha-numeric combinations varied on a rotating basis
    • Model, size or style – vary each from time-to-time or place-to-place
    • Wire or Material coding – using unique color combinations
    • Logos and custom markings – symbols for quick ID of source or content

  • Visible and Psychological Deterrents
    • Warning labels for employees, on packaging, and at point of sealing
    • Pictures and Serial Decals – applied with seal so they must match
    • Post-use employee penalties – Penalties for unreported anomalies, lost seals or damaged seals. Automatic review procedures.
    • Unique material, coloring, or ID – special wire color, fluorescent colors etc.

  • Vendor-Assisted Programs
    • Inventory control and site delivery (managed by your vendor)
    • Staff training and oversight – on seal inspection and procedure
    • Pre-Packaging and control labels – Custom sub-packaging for locations or individuals who handle seals, with inventory control numbers on seal cartons
    • Independent post-use inspection by your vendor or independent lab


Various Security Groups and Standards

Following are descriptions of some of the existing seal standards
and seal related organizations. These can be helpful.

However, other than strength tests the standards can be subjective, and often aimed at certain specific seal uses. They do not rate seals for their ultimate level of “security”.

“Security” cannot be measured or quantified because people’s behavior and capabilities are always part of the equation. This leaves you to choose seals based on real-world factors.


C-TPAT US Customs - Trade Partnership Against Terrorism

This program is a voluntary and comprehensive alliance in which commercial shippers work with US Customs to develop complete cargo security programs for imports. C-TPAT participants are expected to use seals and to demonstrate that a carefully thought out seal and seal control program are part of the overall plan. C-TPAT compliance calls for a seal that passes the high strength test (H) of ISO-17712.

C-TPAT standards of practice can apply to all seals, but a focus is intermodal containers and truck trailers with enclosed box and similar conveyance. Tankers, soft top and flat bed loads present other challenges.

This is a South American program like C-TPAT. It sets strict requirements and standards for its members similar to C-TPAT. The BASC program coordinates with C-TPAT and other international organizations protecting global shipping.

The International Seal Manufacturers Association (Of which American Casting & MFG. is a founding member) is a private industry group. It is an affiliation of top seal producers. This body has worked to develop standards and practices which are intended to help seal users to trust in the seals they are purchasing. To maintain membership in ISMA a company must meet specific standards of both quality and security practices. Currently ISMA members, including American Casting, are certified to ISO quality standard 9001:2015 as written for seal manufacturing.

ISO 17712:2013 Compliance
In addition, AC&M meets  the compliance standards for ISO 17712:2013

 To verify compliance requires:

 Lab Test Classification. A test certificate or report stating that the specific seal model is classified as an “H” High Security seal. (Clause 5 includes five separate tests). The report must be from an accredited third-party testing laboratory with ISO 17712 in its scope of accreditation.

Security-Related Practices Inspection. A certificate, report, or letter documenting compliance with ISO 17712 Annex A, (Seal Manufacturers’ Security-Related Practices.)  The report must be from an accredited third party process review organization.




Technical Assistance, Training, Consulting

If a specific standard is required in your industry, then use it. If not, choose seals that best fit your purpose. Consider what you want to the seal to do. Use hands-on field trials, the knowledge of your staff who must handle the seals, and your common sense.

If you do not have a security specialist in your organization or cannot afford to contract one, American Casting can provide advice at no additional cost to answer your seal application questions.

Assistance can include, finding the right seal, developing tracking procedures, inspecting questionable seals after use, training your staff, and much more.

ALSO SEE : “RECOMMENDED BEST PRACTICES” addendum to this guide.

This document and the accompanying outline of best practices are intended as an introduction to the security seal. It is not a comprehensive or functional protocol and these measures should not be regarded as the sole criteria for establishing a seal use program. We invite those with interest to contact us for more specific and detailed advice on seal requirements, and the use of our seals.

Manufacturer of Tamper Evident Security Seals Since 1910

Headquarters and Factory
51 Commercial Street
Plainview, New York 11803
Tel: 516-349-7010
US Toll Free: 800-342-0333
Fax: (516) 349-8389

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