Prepare for your show by laying the 2 ropes next to each other. Tie them together near the middle with a piece of white thread. Fold each individual rope in half so that the 2 lengths meet with 2 loops. Be sure to hold the ropes by the middle section so that your hand covers the spot where they are connected.
Ask for 3 volunteers from the audience.
Line up your 3 volunteers in a row, facing the audience.
Hand the 2 volunteers on the ends one end of the ropes.
Position the junction of the ropes along the center of the middle volunteer's back.
Take the ends of the ropes from the 2 end volunteers and tie them around the front of the middle volunteer.
Give the 2 lengths of rope back to the end volunteers and ask them to pull on the ropes at the same time. When they pull, the thread will break and create an illusion that the ropes went through the other volunteer.