What does the Knot of Isis mean?

As a knot, however, its symbolism revolves around the idea of binding and releasing, the joining of opposites, and, since a knot secures things, protection. Knot magic was well known in Egypt from an early period; an inscription in one of the pyramids states, “Isis and Nephthys work magic on Thee [Osiris] with knotted cords.”