The Wolfsangel is a z-shaped symbol, sometimes with a small perpendicular central bar. It is similar to the crampon heraldic symbol and the Eihwaz rune, both without a central bar. In military use it stands for defensiveness (German: Wehrhaftigkeit). It was inspired by medieval wolf traps that consisted of a "Z-shaped" metal hook hung by a chain from a metal bar.
The name derives from one part of a historic trap for wolves. Other parts of this trap may also be referred to as a Wolfsangel. The Wolfsangel became a symbol of resistance against oppression after its adoption as an emblem of a peasant revolt in the 15th century. Wikipedia claims that it in early times was believed to possess magical powers.
The Wolfsangel was used by some National Socialist organizations and units. Hermann Löns's 1910 novel Der Wehrwolf, which became a bestseller during the 1930s in National Socialist Germany, had a protagonist who was a resistance fighter during the Thirty Years' War. The Werwolf organization used the symbol.