There are several basic designs of the metal seals; bolt seals, ball seals, and cable seals.
Bolt seals are used to secure shipping containers, trucks, and trailers. A bolt seal used for securing containers must conform to the ISO 17712 high security seal in order to be accepted by customs all around the world in ocean shipping. The C-TPAT[3] (Customs Trade Partnership Against Terrorism) specifies ISO 17712 compliant security seals to be used. Bolt seals are generally closed by hand (by pushing the seal body and head together) and opened with the use of bolt cutters. This gives a strong and secure seal for transportation, while remaining convenient for staff in ports and warehouses.