Trinity Knot ~ Art, Healing, Metalsmithing - The circle often seen around the triquetra signifies the infinite, eternity and protection. Circles are often drawn around Celtic knots to represent spiritual unity with the devine - a connection that cannot be broken.
Pagan Celtic Sleep Blessing (This is the original image. There is a version floating around the internet that is a crude alteration and doesn't have the artist's copyright on it. Please share this version and help spread the word about the original artist's work.)