Show a beautiful hardwood box all around. It has four doors - two in the front and two on top. In addition, show a solid yellow square block. Put the solid block inside the empty box and close the top and front doors. Tip the box. The audience actually hears the block slide to one side. Open one top and one front door to show that the block has vanished. The audience will let you know that the block is on the other side. So, you tip the box the other way and show the other side empty. Back and forth it goes. The block is on the left. No, it's on the right. Finally, you offer to help the audience, and open all the doors. Upon opening all four doors. The block has completely vanished. Show the box all around. They can see right through from front to back and from side to side. The block is really gone.