A threadbone (þráðarleggur). Jónas Jónasson reports that on Icelandic farms many women "busied themselves with sewing and some were remarkably skillful with their needles. Many were expert clothesmakers. They did all their stitching with thread they spun themselves on a spindle and then wound on threadbones [þráðarleggir]: shankbones of sheep or goats. The same threadbone often passed from one generation to the next." These threadbones were "always the favorite holiday gift among women. Often they were colored; sometimes they would have a date inscribed on them" (Íþh123 and n.).
Source: National Museum of Iceland (Þjóðminjasafn Íslands); used with permission. Photo Ívar Brynjólfsson (digitally edited).