An eleglant walnut package with cracks in the foundation and also the lid is shown. The interior is probably big enough to hold on to one single playing card, that when put will block all the passage thru the cracks. The set is completed by a gleaming steel ball bearing. The card in position, the heel bearing is able to come on the lid, finally dropping in to the opening. Though the ball is commanded by the magician to pass, as well as it lets you do, as through the gaps from either side, it's momentarily stopped by the card. The extremely hard happened... reliable through sound.