Resembling an Ankh with bent arms, the Tyet, or Girdle of Isis, is found mainly in Egyptian funerary murals. It most likely represents the flow of menstrual blood from the womb of the Goddess, and its magical properties.The garments of Egyptian gods are frequently depicted with belts in such a configuration. The power of the Tyet is described in a spell in the Papyrus of Ani:
“The blood of Isis, the spells of Isis, the magical words of Isis shall keep this great (or shining) one strong, and shall protect him from whosoever would harm him\do to him such things as he abominateth.”
The knot resembles an ancient charm for menstrual cramps, which involved insertion of a knotted cloth to stanch bleeding. The tyet is also known as the buckle of Isis.
An image of Mary Magdalen wearing a similar Girdle, possibly hinting at some special symbolism: