In industry, the term “security seal” is a broad descriptor for a large class of tamper-evident security devices. Some of the best known security seals are on consumer products such as condiment jars and pill bottles. These seals usually present as foil wrappers or push-top lids. Other security seals are much more complicated, often involving thermal printing, laser engraving, and seals for large shipping crates and valuable or sensitive merchandise.
Regardless of what it looks like, a security seal is designed for but one primary purpose: content restriction. Manufacturers use seals whenever they want to keep the contents of a package isolated and contained. The reasoning and the means of the sealing technology may vary depending on the interests at stake.
On food products, a security seal is usually designed to protect against tampering. These kinds of seals usually take the form of tight-fitting inserts situated just below container lids. Vacuum-sealed lids that pop when opened are also forms of the same technology. The goal here is to prevent people from altering the contents of the product, removing any portion of the product, or adding anything to the container.
Security seals are used in many other contexts, as well. In land shipping, security seals are usually tapes or package seals that prevent boxes from being opened before they arrive at their destination. Plastic zip ties that secure suitcases and zippered parcels serve the same purpose.
Other seals are designed to hold materials together. Shipping pallets are often shrink-wrapped to prevent both theft and content shifting. Stretch wrap and plastic binding tape is also commonly used to seal and secure multiple parcels during transport.
At a very basic level, a lock or bolt is also security seal, since it protects internal contents from access by the outside. Sophisticated criminals often have ways of circumventing these sorts of protections, however. Serious shippers usually invest in either specialized locking tools, or look for more particularized locking measures.
Metal tags and bindings are often used to seal shipping containers or cargo crates. This sort of security seal is usually engraved or stamped with a particular serial number that cannot easily be replicated or replaced if destroyed. Truckers, naval ship operators, and train freight operators can also use these numbers to track shipments.
Cargo crates and shipping containers can often be sealed with lead or wire, as well, which can make premature access all but impossible. These sorts of seals are particularly popular for sensitive scientific material, including bacterial strains and other hazardous chemicals. Cap seals and metal seals can usually be engraved with serial numbers for easy tracking, the same as metal tags and cargo seals.
Confidential documents may also be secured with a security seal. Security labels are often custom printed on highly adhesive paper that cannot be broken undetected. The most sensitive documents often require thermal-printed seals, many of which will change color if tampered with.