Cylinder seals are small spool-shaped objects used in the ancient Near East to mark ownership and seal objects behind doors or in jars, boxes, or baskets. They were usually made of stone and carved with designs that appear raised when rolled over wet clay. Cylinder seals were also worn as pendants or bracelets and were believed to possess magical powers. They were first made about the time that writing was invented (3500 B.C.) and continued to be made up to about 500 B.C. Thousands of cylinder seals have survived because they were made of strong materials - usually stone, but also shell, bone, ivory, glass, and metal.