Three Shell Game with Coins and Boxes
Start with three boxes, 2 are empty.
They take a look inside box 3 and fills it with Half dollars.
The Half dollars vanish from box to box, re-appearing at your command!
So you set an empty box to one side. Two boxes, only one has Half dollars inside.
Still the coins jump from box to box, and end up in box 3 set to one side.
The boxes do all the magic!