​The Ultimate Security Seal Guide

​The Ultimate Security Seal Guide

Posted by Steve Diebold

The Ultimate Security Seal Guide

What’s this guide about?

American Casting & Manufacturing offers dozens of different security seals and products for your security needs. If you’re not familiar with security seals, understanding and finding the right product can be daunting. If you’re a long-time customer, then you know how important it is to understand the capabilities of security seals.

We put together this guide to help you learn about the variety and applications of our security seals.

The history of security seals

The origin of security seals dates back at least to the days of Pharaohs and Kings when official seals were carved in stone, metal or wood. The “seal” was pressed into melted wax, used to close documents and containers of valuables while in transit by messengers. The impression of the seal in wax, if disturbed, or replaced with a forgery, would indicate to the receiver that the document had been opened or tampered. The job of inspecting these seals often fell to a scribe or other servant who knew the seal intimately and could readily see a forgery or tampering. The modern security seal serves essentially the same purpose -- just with far more advanced tactics.

In the late 19th and early 20th century, several companies introduced various mechanical seals to secure rail cars, meters, and bank or courier bags. That business continues. American Casting & Manufacturing is the only remaining U.S. owned and operated full-line security seal maker from the last century. Some of the original U.S. makers are still in business today, but manufacture largely outside of the country.

The expansion of security seals and their uses

Originally, there were only a few seal types (mainly made of lead, or tinplate steel), with some variations. Through the last century, uses and number of security seal types proliferated into thousands. Growth in trucking and over-the-road delivery spawned many more seals and seal uses. Then international ocean containers created an entire industry of heavy bolt and cable devices to secure the doors. Plastics, heavy metal, cable, and wires are now used to make mechanical seals ranging from small and simple lightweight plastic security seals to large iron and steel devices that serve as barriers to unauthorized opening.

More recent developments include advanced electronic devices with RFID data recording and monitoring functions, remote reading, GPS tracking and more. There are also new adhesive labels and tapes, holographic images, thermal activated inks, and high-tech printed adhesives that leave an impression and/or destroy a printed pattern if the security tape is removed.

Security seals, what are they good for?

Security 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. Early seals were intentionally made to be easily cut open after use. By around 1980 the added dimension of a high strength barrier seal became popular in transportation. Now, some security seals function both as a strong disposable lock and a seal -- to provide evidence of entry or violation.

When security seals are found tampered with or violated, it is the tampering indicators which allow the user to begin investigating, ultimately catching and stopping the violator. The seal does not stop entry. But a higher strength security 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: opening and closing and hiding the breakpoint to fool the observer, substitution of parts, modification of marking, or substitution of whole (clone) seals. The initial discovery of tampering may take place when the seal is cut and taken out of use. It may also be found on examination of the seal after it is opened by the user and checked at another location. If not examined by an informed person, tampering with or violation of the security seal may not be discovered at all.

Once discovered, the process is normally one of systematically narrowing the time and/or place the violation occurs. This tells an investigator who could potentially be violating (or attempting to violate) a secured container or device.

Stronger security 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 tamper evident seals can help catch or deter thieves.

Terminology and classifications

There are two general seal types, but three categories in today’s official government terms. The two main types are:

Indicative security seals serve the function of providing tamper evidence but are easily broken or cut open with light tools. These are also sometimes called tamper-evident seals.

Barrier seals are higher strength security seals that can provide tamper-evidence and serve as a one-time lock to slow down and deter theft or vandalism. They require large tools to cut open.

Many still refer to all seals as Security Seals. It is a simple and accepted generic classification. It helps in common language to distinguish this type from seals used for other purposes not related to security and tampering. (ie o-ring seals and the like)

ISO-17712 standards for seals use three specific classifications, according to strength. They are:

Indicative seals include all light duty seals that can be removed by hand or with basic tools such as shears or common household cutters. Indicative seals are the most used and found in the most applications. These include almost any closure, like totes, bags, wheel carts, ballot boxes etc. This also applies to stationary closures such as utility meters, valves, cabinets, lockers, bins, and cages.

Security seals are of intermediate strength and require a stronger or larger tool and more effort to cut open than indicative seals. Added strength can help avoid accidental breaking or easy entry, without tools.

High security seals is a term now applied to barrier seals that are the strongest and most difficult to cut open. Larger and stronger tools are needed to cut them open. The standard testing for this category requires resistance to specific levels of pull, bending and crushing.

Refer to the standards of ISO-17712 and C-TPAT for more on this.

Seals tested and certified to meet the High Security standards of ISO-17712 are stamped with the letter (H) and the identity of the manufacturer. Ocean containers, rail cars, and long-haul trucks are the most common commercial uses for barrier security seals.

While useful in general, these three classifications are limited to lab tests for strength and can exclude good seals from being considered for many applications. Additionally, the terms may confuse the buyer about the real level of security they can get for their specific application. Much depends on the specific design, how it fits the application and especially on how -- and how well -- the security seals are applied, controlled and examined. A very strong or well-made seal has little security value if it does not fit or is not carefully documented and inspected throughout its use by reliable people.

Countering terrorism

With today’s concerns of terrorist acts, security seals have become a more noticed tool to identify a container of goods opened after it was sealed at its loading point. But, the added challenge of immediacy requires a much higher degree of knowledge, control, and attention to the seal throughout its use. In addition to more control and inspection, immediate discovery may also require the use of more than one device and method.

International standards for the production and practices in the supply of security seals are being regularly updated. The latest ISO-17712 standard is discussed later in this piece.

Standards for electronic seals (E-Seals) plus recording and tracking devices are under consideration. Several designs are in limited use, mostly on ocean containers. Their value as anti-terrorism tools is still being assessed.

How effective are security seals?

Seals alone cannot protect cargo containers and other closures from access by motivated people who intend harm, nor can any technology. It is unrealistic to expect absolutes.

However, each step toward improving design and application of tamper evident seals and related technologies improves the odds of detecting and preventing loss and reduces points of opportunity. This is what security measures are intended to accomplish.

We have over 105 years of global experience in the seal industry. We supply security seals and other devices to almost every segment and enterprise of industry, government, and the military. While each situation is unique, there is one overarching and often misunderstood reality of the effectiveness of security seals.

All Security Seals can be defeated.

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.

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

What makes an effective tamper evident seal?

For a security seal to be effective, there must be a reasonable level of reliability upon the points of locking and opening.

What matters most is who is handling the seals and how they are handled. Seals are used to great benefit in countless applications every day. One can argue which ones work best (or don’t work) for a given use, or even if they are necessary for your purposes. But, if you use security seals, it is more important to deal with how they will be handled. This is primary and helps determine 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 tamper evident seals effectively is a far greater challenge than finding a design that fits.

Uncovering tampering of a seal requires a reasonable level of reliability when it is locked and when it is taken out of service. That reliability depends partly on the mechanics, but even more on human behavior. There are physical, psychological, procedural and regulatory steps that can and should be part of the whole sealing process.

Theft, smuggling, sabotage, and other nefarious activities are human behavior issues. They must be met with a flexible and unpredictable approach, by 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 and realities of the situation will not get the job done.

Techniques and countermeasures to maximize effectiveness

There are many techniques or “tricks” which will help to make a security seal more effective. All must be backed by real consequences and personal responsibility. It is important that seal users are always evaluating and finding their own measures that will best enhance the seals’ worth. Outlined below are some general steps that can be taken to make tamper evident seals useful and effective.

●Layered Technology

○Combining devices, security seals plus tape, multiple matching labels, or multiple tamper evident seals

○Enhanced Visual ID, - adding unique mark or indicator at time of locking

○Segregated sealing (seal separate from a barcode, RFID tag or other identifiers)

●Variations Within Standard Security 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 – unique multiple color combinations

○Logos and custom markings – symbols for a quick identification of source or content

●Visible and Psychological Deterrents

○Warning labels for employees, on packaging, and at the point of sealing

○Pictures and serial decals – applied with the seal so they must match

○Post-use employee penalties – penalties for unreported anomalies, lost or damaged security 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 tamper evident seals and inventory control numbers on seal cartons

○Independent post-use inspection by your vendor or independent lab

Performing up to the current seal standards and programs

Various classifications and standards for security seals have existed or are being developed, each addressing certain aspects of seals. These are all reference points for understanding seals and their evaluations. However, users are ultimately challenged to choose tamper evident seals based on more criteria that are put forth in any existing standards. Meanwhile, there are programs completed or underway to evaluate the seals and practices, mainly in seals for containerized cargo transported internationally.

Current security seal standards


The latest ISO standard for security seals is ISO 17712:2013 --including Clause 6 and Annex A

This standard still sets three categories of seals from “High Security” to “Indicative" as listed in the earlier section. It also requires specific test standards, used in verifying High Strength (H) seals. Further, it requires standards and practices for security seal manufacturers. These relate to production, inspection, quality control, internal evaluation of tamper resistance, documentation, handling, and storage of tamper evident seals.

Strength tests must be performed by a certified testing laboratory when testing for seals classified High Strength (H). The other seals in category Security (S) and Indicative (I) are seldom tested independently for strength. To test them for strength would only verify they are not strong enough to be in category (H).

Conformance and independent auditing under Annex A provide assurance that a manufacturer follows accepted practices required for compliance with the ISO standard for seals in all categories.

American Casting & Manufacturing is a member of the International Seal Manufacturer’s Association (ISMA) and also participates in the ISO committee responsible for seal standards.

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

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


BASC 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 & Manufacturing is a founding member) is a private industry group. It is an affiliation of top security seal producers. This body has worked to develop standards and practices which are intended to help seal users trust in the tamper evident 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 9001:2008 as written for seal manufacturing.

In addition, they meet the compliance standards for ISO 17712:2013 according to the “Compliance” supplement that can be found on the ISMA website.

Selecting the right security seals for the job

Determining your security seal needs depends on a few factors:

●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 the seal type with the appropriate level of strength and security

First consider if an indicative or barrier security seal is required, and what strength level is best. Also, consider costs relative to the security risks for your application (It is quite possible to invest too much or too little in seals).

●Use a manageable locking system

The system should be within the capability of the facility and the person(s) applying and inspecting the seal. Also, if special tools are required, consider both cost and availability of tools. Sophisticated or complex systems without adequate facilities and staff are not effective

●Materials should be suitable for the environment where the tamper evident seals are to be used.

●Make sure the seal has capacity to contain all of the information needed

Information may include as little as a control number or, such things as logotypes, product codes, barcodes, and even complete tracking history and load manifest data.


●While we recommend American Casting & Manufacturing, it is important to find a company who (like us) has the credentials and will work with you as a partner in developing a comprehensive program including good practices.

●Qualified seal sources like AC&M will have a known history of reliable service and suitable industry credentials for evaluation by potential buyers.


●If you do not have a security specialist in your organization or cannot afford to contract with a professional consultant, we recommend consulting us or your American Casting Representative. American Casting can provide advice, at no additional cost to answer your seal application questions.

●Assistance can include: finding the right security seal, developing procedures, inspecting questionable seals after they are used, training your staff, and much more.

●You may also use a qualified security consultant to help implement or update your sealing program. Consultants or in-house security specialists are recommended for anyone with complex and very high-risk conditions.