High Security Seals delay or obstruct intrusion and have been designed to conform with world customs and ISO security seal standards. ISO is a compliance standard from the US Customs-Trade Partnership Against Terrorism (C-TPAT) and the World Customs Organization’s Framework of standards. To be classified as a High Security Seal, a seal must have obtained an ISO 17712 rating. The ISO 17712 rating provides “uniform procedures for the classification, acceptance, and withdrawal of mechanical freight container seals. It provides a single source of information on mechanical seals which are acceptable for securing freight containers in international commerce.” Seals that belong to the High Security level are sometimes called "barrier seals". They are made of different metals or metal alloys, meaning they require special tools to be opened, such as bolt cutters or pliers. Cable seals and bolt seals also fall into this category. Designed to deter opportunistic theft of high value goods, they also can often be branded and numbered to improve tamper resistance and provide excellent security for containers.