The other great invention of this period was that of armorial bearings, properly so called. Devices painted upon the shield were common in classical times. They are found ordinarily on the shields in the Bayeux tapestry, and were habitually used by the Norman knights. In the Bayeux tapestry they seem to be fanciful or merely decorative; later they were symbolical or significant. But it was only towards the close of the twelfth century that each knight assumed a fixed device, which was exclusively appropriated to him, by which he was known, and which became hereditary in his family.