Rogue's yarn

yarn of a different twist and color from the rest, inserted into the cordage of the British navy, to identify it if stolen, or for the purpose of tracing the maker in case of defect. Different makers are required to use yarns of different colors.

See also: Rogue

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
In the 1800s, the practice was so rife the Navy spun a coloured strand into their rope, known as 'the rogue's yarn'.