Magnetic Sticks - demonstrate that magnets have always two poles - sticks placed by the same poles repel each other, but when stainless steel ball is put between, they attract each other, the effect being caused by magnetic domain re-ordering in balls.
The iron ball inserted between poles of different signs (the upper figure) et magnetised in a "normal" way, becoming a two-pole magnet (N-S), with the axis oriented in the direction of external magnets.
The ball between two poles of the same sign "accommodates" (the lower figure) its magnetic poles in a way to be attracted by both external magnets. We find the "missing” poles on a plane perpendicular to the axis of magnets.
You can create amazing constructions out of those colourful sticks. But at least every two magnets you have to place a metal ball between them. If you don't, the whole thing will fall apart.
Now think carefully: magnet either repel each other or attract each other. If one end of the stick attracts another stick, the other end of the first stick should repel the second stick. And it would be so if we didn't place the metal ball between the poles.