The magician displays two bars with four cords running through them.
The bars are held with a little gap
The two middle cords are the same color,
The two ends cords are different colors
The Performer now draws the bottom bar downwards.
That shows that the cords run freely through the holes of the bars.
Now the two bars are at two ends of the cords.
He then claims that the end cords will jump from one end to the other
He then passes the bar behind his back and the cords have changed color!
He repeats and they change back!
Then passes it behind his back again, and the cords on the outside are in the middle,
the cords in the middle went to the outside!