The size, Хитрая гайка

18-September-2016 Sunday
Found this in the attic. I would like to know what it is for and where it can be applied?

Found this in the attic. I would like to know what it is for and where it can be applied? - What's this?, Photo, screw, The size,

screw The size Photo Хитрая гайка What's this?

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