What is a Turkish Knot

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What is a Turkish Knot? Here I look at Turkish knots in a Hamadan Rug fragment.

Turkish knots are seen most commonly in Turkish rugs. But in Persian Rugs the knot is very important because it can help us attribute what a rug is and where it is from.
Common Persian Rugs that have Turkish knot include:
Tabriz Rugs
Senneh Rugs
Hamadan Rugs
Bijar Rugs
Zanjan Rugs
Bakhtiari Rugs