The civilizations of ancient Mesopotamia believed in keeping a written record of everything. However we believe that not very many people actually knew how to write using cuneiform (the written language of Mesopotamia). If you did not know how to write, you might hire a scribe to write for you. But if you just wanted to sign your name to something, you might commission a cylinder seal.
A cylinder seal was an oblong object like the one pictured above. It had pictograms on it that were unique. Each cylinder seal was different. Signing with your very own cylinder seal let people know that it was you who had signed this document or tablet. Signature by cylinder seal made a document legal and binding. Thousands of these seals have been found, so we assume that they were common among the business and working class.