Cylinder seals were rolled onto clay tablets or clay sealings for identification, verification or authorization, much like a modern signature or official stamp. The design, carved in the negative, left a positive impression when rolled out.
The Mittanian seals with the most elaborate and best carved designs are known only from their impressions. Among these are the seals of Saushtatar, king of Mittani, Ithi-Teshshup, king of Arrapha, and Ar-Shali, a Nuzi official, besides numerous uninscribed seals. The seals that have been found were made of two types: composition (sintered quartz paste covered with glaze) and hard stone.
Seal inscriptions can provide information on seal ownership and use. For example, the seal of the Mittanian king Saushtatar was used as a dynastic seal by his descendants, while Ar-Shali's seal survived for several generations as an official seal.