You may have picked up a book about runes or purchased a rune set that includes a "blank rune", "Odin Rune" or "Wyrd Rune". This is a very strong clue that author is not an authority on runes. There is no historical evidence that runemasters of old ever used a blank rune. It's self-evident because a rune is a symbol, not the token that carries it. Have you ever seen a blank symbol? Of course not, that's an oxymoron.
In runic writing, a space, a single dot (.) or two dots (:) may break the symbols or words. Sometimes no break was used and the rune symbols all run together. Runic writing can run from left to right, or from right to left; some times even from top to bottom or the opposite. It makes interpretation of runic writing difficult, especially since runic symbols and the languages changed over the years. Even the futharks changed over time. This is why ancient runic inscriptions are often often obscure or may be interpreted several ways. What follows is a "nid rune", a harsh magical script curse, that demonstrates the breaks.
Regardless of the language used, or the futhark used, or the style of writing used, no one ever used a "blank" rune.
We can thank Ralph Bum and his commercially popular but historically inaccurate Book of Runes for the introduction of the "blank rune" in the 1980's. While Blum's books are the most readily available rune books found in bookstores, use of his flawed interpretations reveal the user as a novice and lacking in knowledge of true runelore. If you've bought one of his books or another of similar ilk, keep the runeset (and save the blank one in case you lose another) but toss the book in the trash and get one of the books I've recommended instead.