Gleipnir

In Norse mythology, Gleipnir was the third chain used to tie up Fenrir, the wolf. Fenrir was the son of Loki and Angrboða, the giantess. The first two chains, named Lædingr and Dromi, were forged by Thor and did not hold him. Gleipnir was created by the sons of Ivaldi and did hold Fenrir. It was as thin as spider's silk. Gleipnir was made from six things: 
This was probably used to explain why all of those things are impossible.
The gods lured Fenrir to the island of Lyngvi. They challenged him to be bound by Gleipnir. To show Fenrir it was no trick, Týr put his hand in Fenrir's mouth. When he could not break Gleipnir's grip on him and they refused to let him out, Fenrir naturally bit off Týr's hand. Fenrir was to remain bound by Gleipnir until Ragnarök (the final great battle of the gods).