A seal is a wax or other item used to close a letter, parcel, or other item, to indicate whether or not the item has been opened since the seal was applied. Seals are no longer commonly used. Seals were used both to seal the item to prevent tampering, as well as to provide proof that the item was actually from the sender and is not a forgery. To seal a letter, for example, a letter writer would compose the letter, fold it over, pour wax over the joint formed by the top of the page of paper, and then impress a ring, metal stamp, or other device.
A seal is also a device used to create such an impression (which is sometimes called a "sealing"). Seals were already used in the earliest civilisations and are of considerable interest in archaeology. In ancient Mesopotamia seals were engraved on cylinders, which could be rolled to create an impression on clay e.g., as a label on a consignment of trade goods. From Ancient Egypt seals in the form of signet-rings of kings have been found. In the Indus Valley Civilisation, rectangular seals were used to label trade goods and also had other purposes. In modern Japan, the hanko signature-stamp is still in relatively widespread use.