The symbol of the Walknut has long been the subject of debate as to its meaning and use. The above is one of the few depictions we have of this symbol, so we must use what we have to decipher the meaning. On it is found an upright tree with a curved tree leaning between a branch of the trunk; from this curved tree hangs a warrior holding a shield. This, of course, could well be a sacrifice of the warrior to Woden, since we find another figure holding a spear, leaning over yet another who appears to be laying across something that is not really clear as to what it is. Another smaller figure appears to be leaning over a stone (Sacred Stone?).
The tips of the three triangles of the Walknut are pointing downwards towards the smaller figure and the standing stone. There are three birds in the picture, but what they are is not really clear, though the central one may be a Raven. One bird is flying over the Hanging-Tree, another over the Walknut, and the third is behind the figure with the spear (Woden), and this one is not flying.
That the hanged figure is a warrior may suggest some form of sacrifice that takes place after a battle, where the losers were sacrificed to the God of the Hanged; this was done, it seems, at the Battle of Teutoberg Wald where the remains of Varus' Legions were sacrificed to Wotan.
The name Walknut can be rendered Wal-Knot or 'Knot of the Slain', though the Aryan Root *wal- means 'to twist,' 'to turn', or 'to coil', thus suggesting 'spirit' as the true meaning. But we can also render this as Walk-Knot which means Wolf-Knot and clearly suggests the god Woden as the Wolf-God.
In the picture there are two tall figures and two small figures, and it is quite usual to see some of the taller figures as gods, whilst the smaller ones can be seen as humans. In which case both the figure who is hanging, and the figure holding the spear, are Woden. Of course, this scene could be that of some kind of Initiation Rite, since Woden's Initiation consisted of his hanging for Nine Nights upon the Sacred Gallows-Tree, Iggdrasil. This is the 'Wolf-Tree'. Such a rite is based upon a 'Death and Rebirth', as are all Initiation Rites, where the candidate 'dies' (sheds his old identity) and is 'reborn' (takes on his new identity).
I don't think we should consider our forefathers as some form of 'primitives' whose artwork was also 'primitive'. The knot-work on this is quite fine and obviously has meanings that could be symbolic. You will notice that the two taller figures are lower down than the smaller ones, which to me suggests the artist used this technique to show the smaller figures being a little further back from these. This singles out the two taller figures as facing each other; it is significant that the right-hand figure does not actually hold the spear, which is seemingly in mid-air behind him. He seems to be addressing the Hanged Warrior, whose feet are noticeably on the ground.
It is possible, when using a piece of cordage formed into the shape of the Walknut, to get from this a 'slip-knot', which suggests once more the 'Hangman's Noose'. Since we find the name 'Walhalla' as the 'Hall of the Slain' then there has to be a connection between 'Walhalla' and 'Walknut'. Both are to do with the 'slain', but both are also connected to the Aryan Root *wal- and thus to the 'Spirit of Man'.
It may well be important that the Walknut here is seen pointing downwards, and may thus represent the descent of Spirit into Matter. In which case the smaller figure on the right can be seen as 'dead', and the one on the left as being 'reborn', having become the 'Twice-Born' after going through such an Initiation Rite. This might be underlined by the bird that hovers over the Walknut Symbol, this being symbolic of the 'heavens' and the 'divine'. The symbol in the right-hand corner is very much like a Fylfot-Swastika Symbol, but it has five arms; our own Milky Way Galaxy appears to have five-arms. This to me suggest some form of 'Galactic Event', and together with the idea of a 'descent into matter' we come close to the idea of an Avatar incarnating into matter.
The bird behind the Spear-God may well be a dove, and if so the name of this bird means 'diver', but was not originally given just to the bird we know of as a dove. In the New Testament this is used of the 'descent of the Dove' into The Krist who is thus and 'Avatar'; clearly at this point he takes upon himself an Archetypal Myth which he needs to fulfil in his lifetime. We could also see in this scene the transformation of the Hanged God into the Crowned and Avenging Son. This, of course, is a galactic event, hence perhaps the curvilinear five-armed Fylfot-Swastika above the scene.
The second tree that has its trunk through the first has a much different design than the tree that stands upright. There is a hand-like shape at the end, whose design suggests a kind of 'Tongue of Fire'. This is a kind of 'ghostly' shape reaching out towards the Walknut Symbol. One point of the Walknut points to the smaller figure on the left, the other to the standing stone that he seems to be reaching out to. What came into my mind here is the god Ingwe, a Fire-God who is brought to life by the Friction-Fire, and whose clear links to The Krist should be borne in mind here.
These are my own personal interpretations and are based alone on intuition and insight, and have no scholarly basis I am afraid. We have to remember that although we refer to Iggdrasil as 'The World Tree' it is in fact the 'Cosmic Tree' and represents the Cosmos or our own Milky Way Galaxy (hence why it is a 'White Tree') in particular. The self-sacrifice of the Hanged God was a cosmic event, just as the transformation of the Hanged God into the Avenging Son is also a cosmic event.