According to one interpretation, that of H. R. Ellis Davidson in Gods and Myths of Northern Europe (ISBN 0140206701) (p. 146), the valknut —
is thought to symbolize the power of the god [Odin] to bind or unbind [a man's mind] ... so that men became helpless in battle, and he could also loosen the tensions of fear and strain by his gifts of battle-madness, intoxication, and inspiration.
The symbol of the valknut plays a role in neopagan faiths drawn from Norse mythology. In these, it represents the interlinking of the nine worlds, and the spirit and power of Allfather that binds and pervades them all, and it is worn by those who chose to give themselves to Odin.
One Ásatrú website [1] (http://hometown.aol.com/_ht_a/xcalabr08/himinbjorg.html) says:
The nine lines symbolize the nine worlds of the Norse tradition. The three triangles are said to represent the three realms of existence, and the ability to travel among them. The symbol is also associated with Fate, each triangle represents the Past, Present & Future, and their influence to each other.
The valknut is composed of three interlinked equilateral triangles.
To the Norse people of Scandinavia, a drawing of the Borromean rings using triangles is known as "Odin'striangle" of the "Walknot" (or "valknut" -- the knot of the slain).
The symbol was also carved on the bedposts used in their burials at sea.
The presence of the valknut on Viking Age crosses in England and on the Brompton hogback hints at a retention of this element of heathen iconography among the adherents of the new cult.
If the valknut does 3124 stem from the cult or mythology of Odin, then it must represent something that cannot be given a pictorial rendering, either because of a taboo or simply because it just cannot be pictured in anything but an abstract form.
It is interesting that in England the use of the valknut seems to have died out with the establishment of Christianity and the consequent decline of heathenism.