Cylinder seals are small cylinders, generally made of stone. Most of them have a hole drilled through their length so that they could be worn on a string or pin. They are engraved with a design so that when they were rolled out on clay they would leave a back-to-front impression of the design in relief.

Cylinder seals were probably invented in southern Mesopotamia about 3500 B.C. and were used until about 300 B.C. They are found in all countries where cuneiform writing was used. Stamp seals were used even earlier, from about 6000 B.C., and continued in use long after cylinder seals went out of fashion.

When people wanted to keep things safe, they would tie the storeroom door to a peg in the wall and put a lump of clay over the string. They would then roll their cylinder seal over the clay to show they had sealed the door. In order to open the storeroom, the lump of clay had to be broken and the string untied or cut. Jars of wine, boxes, bags and baskets could be sealed in the same way. This did not stop people from stealing, but at least it would show that they had. Seals were also used for sealing legal contracts and business documents which were written on clay. Many old impressions of seals have been found but most of these are broken.

There are many different pictures on the seals and from these pictures it is possible tell when and where the seals were made. The images carved on the seal also provide evidence of what people wore, what sorts of animals they had, what their chariots, boats and buildings were like, and especially what they thought their gods and goddesses looked like. Seals represent some of the finest works of art from Mesopotamia.

Although cylinder seals were used only in the Near East for just over three thousand years, stamp seals have been used ever since they were first invented. They are still being used today. Royal charters are sealed. In China and Japan stamp seals are used with ink as a signature. Passport stamps and the franking of postage stamps are also a form of seal.