Half pulling it out of the case matchbox, show it to the audience. Turn boxes with the opening facing downwards and slowly move it back. Here are the boxes appeared on the other side of the case, but again hole up. If you haven't turned! You can repeat all again. The effect will be the same.
What is the secret? Boxes cut into two equal parts. One of them turn up, the other upside down. In this position the two parts are glued together with a thin strip of paper (in case you can't see it). No matter how many times repeated demonstration, the boxes will always roll over.