Length is 12 inches
Meant initially as a “triangle,” it was used to refer to various three-cornered shapes.
Sometimes, the traditional triquetra symbol is accompanied by a circle.
In the Celtic tree of life, the Celts favored that everything in this world came in threes.
Three stages of life: life, death, and rebirth
Three elements: the Father, the Son, and the Holy Spirit
Three domains: earth, sea, and sky, past, present, and future.
The triquetra is sometimes drawn weaving around a circle, symbolizing the unity of the three parts. The circle, in many belief systems, is a symbol of eternity. Whether it is the eternity of God’s love or the eternal circle of life itself, the circle adds even more weight to the significance of the triquetra. So, whether you’re Christian, Pagan, or somewhere in between, there’s a good chance that the Triquetra could hold some kind of personal significance and no one else can dictate what it should mean to you. (source)