Snake Knot（蛇结）

1.  One cord with two-way, the up one is green cord, the down one is red cord;

 2.  Use the green cord make a clockwise circle, then use the red cord through this circle;

3.  Use the red cord wrap the first clockwise circle, then make an anticlockwise circle; According the arrow and  tight these two cords;

4.  Repeat step 2 and step 3, until the length what you need.