The Valknut is probably the most known and used symbol (as well as the Mjölnir) by the neo-pagans who follow and practice the old Norse pagan traditions. However, most people don't know it's meaning, sadly. The word Valknut is a neologism, created in modern times, formed by the combination of "valr" (the dead or the slain" and knut (knot). This symbol has many connections with the other symbols I have written before, this is a symbol of three interconnected triangles. These triangles may be joined in two ways, and I will place images below.
It can either be as Borromean: