However, I note this not only because it is the first time we see the Runes in the story, but also because Byock points out (reminds us) in his own notes in the book that Runes "had both practical and magical uses." In fact, this story presents both aspects of the Runes and that is where I want to focus.
Brynhild's expression of the Runes presents their magical side and talks of spells and how to use them properly. Aid Runes, for instance, are used to help with child birth and she claims that they are to be cut into the mother's hand and then the Rune carver must take her hand into his/hers and "bid the Disir not to fail".
In another verse, she mentions Tyr when speaking of victory Runes and even says that they should be cut on the sword's hilt on the blade's center ridge. She never calls this Rune Tiwaz, yet we know that Tiwaz was carved on many swords and is Tyr's Rune. To be sure, one of the enigma's that surround the Runes is that they are not mentioned by name in many instances.
There is an exception to that in Brynhild's Rune knowledge though. When discussing ale Runes and the goal of keeping a neighbor's wife at bay, she states that ale Runes are to be carved on your horn and the back of your hand... and Naud (Nauthiz - the need Rune) on your fingernail. This is one of the few places where a Rune is actually named, even then, she may just be saying "the need rune", but we know that is Naud (Nauthiz).
Using the Runes for "practical" purposes, as opposed to the implied magic of Brynhild's Runes, Gudrun carves a message in Runes to warn her brothers that her husband, King Atli, plans to take Sigurd's treasure from them. The king's messenger reads the message and changes the Runes to make it appear as though Gudrun wants her brothers to accept her husband's invitation. With the letter Gudrun sends a ring tied with wolf's hair, which her brother, Hogni, initially sees as a warning until the messenger gives him Gudrun's note, which he altered. Although Hogni does not recognize the changes, his wife, Kostbera does. She can tell the Gudrun's message has been falsified.
Interestingly, the story says that Kostbera uses her wisdom to discern what the Runes truly said. When she figures it out, she wakes her husband to tell him not to go on the trip to see King Atli. She says:
The Saga of the Volsungs is not a happy one, but it does offer concrete examples of both uses of the Runes, along with dragon slaying, great battles, and great deceit."You cannot be very skilled at reading runes if you think your sister has asked you to come at this time. I read the runes and wondered how so wise a woman could have carved them so confusedly. Yet, it seems that your death is indicated underneath. Either Gudrun missed a letter or someone else has falsified the runes."