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Guide wires are frequently used in various endourologic procedures to access the upper as well as lower urinary tract. Flexible guide wires have lesser complication rate of tissue injury as compared to stiff guide wires. Flexible guide wires are however more prone to bending and kinking due to their mechanical properties. We report an unusual complication of knotting of flexible guide wires during endourologic procedure and the trick to remedy this problem. We have also discussed the structural design and mechanical properties of commonly used guide wires.