Performer displays a cylindrical brass block, and a brass tube closed at one end into which the block just fits. Also displayed is a metal rod. The block and tube both have a hole across them. When the block is placed in the tube, and the rod pushed through the hole, the block is locked in place in the tube. It cannot be removed. Yet the performer causes the block to penetrate off the metal rod with a mere tap of his hands. You get the brass block, the tube and the metal rod.