In East Asia, many people sign documents with seals—for instance, the chop in China or the hanko in Japan—in the form of wood, horn, or rubber cylinders. Similar devices were used in Mesopotamia in ancient times by the Assyrians and Hittites.
In the Middle East, cylinder seals were typically made of stone, although other materials, such as bone, ivory, glass, metal, wood, or clay, were also used. The unique inscription carved on the seal left a raised impression on a clay tablet, identifying the signer.
Cylinder seals were used to prove authenticity or ownership. In addition, like signatures on contracts today, they were used to indicate participation in and assent to a transaction. Seals were also used to prevent or at least reveal tampering, presumably in a similar manner to the thread trick used to this day.
In addition, seals of certain materials, such as lapis lazuli, were imbued with magical properties and used as amulets to ward off bad luck and bring good fortune.
Some information from http://www.smith.edu/hsc/museum/ancient_inventions/hsc03b.htm. | 
