During the Middle Ages most burghers and peasants had merchant's marks or house marks that were used for marking ownership and as a means of personal identification. These marks are older than heraldic tradition. They are mostly simple compositions of straight lines suitable for being scratched in wood or other materials. They have a similarity to runes and some marks consist of the initials of the owner. Later merchant's marks also incorporates Latin letters. In the beginning these marks were displayed without a shield but during the Middle Ages it became common to draw them inside a shield. Merchant's marks were used by burghers until the 18th century and for about a century longer by peasants.