Cut several lengths of yarn about 2 1/2 times the desired finished cord length. Fold the strands in half to form two equal groups. Anchor the strands at the fold by looping them over a doorknob. Holding one group in each hand, twist each group tightly in a clockwise direction until they begin to kink. Put both groups in one hand, then release them, allowing them to twist around each other counterclockwise. Smooth out the twists so that they are uniform along the length of the cord. Knot the ends.