The present invention relates to a fixing device for fixing to timber, plastics materials and friable substrates, the fixing device comprising a shank (1) having a first end and a second end, the shank comprising helically extending first (4), second and third parallel threads, wherein the first, second and third parallel threads are upstanding from the shank and are in spaced part arrangement to each other and the height of each thread above the shank is equal to the other.