My Celtic Knot design leather dog collars are so popular I've given them their own category here on my website. Having always been interested in Celtic knotwork, I saved you a job and looked it up.
So what are Celtic knots? Celtic knots are a variety of knots and stylised graphical representations of knots used for decoration. These knots are best known for their use in the decoration of Christian monuments and manuscripts, such as the 8th-century St. Teilo Gospels, the Book of Kells and the Lindisfarne Gospels. Most are endless knots, and many are varieties of basket weave knots. (origin: Wikipedia)