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.
Regardless of the language used, or the futhark used, or the style of writing used, no one ever used a "blank" rune.(Sunnyway)