Blocks Off! - Ickle Pickle

6 different colored wooden blocks are placed side by side into a rectangular box completely filling the interior.  They can be seen in their correct order through holes in the top of the box.  A large dowel is pushed through one end of the box and the center holes of all six blocks and out the other side "locking" them in place in the box.  Yet when the box is opened and inverted a spectator's choice of two blocks magically penetrate the dowel and drop to the table below!