You show 5 cards with the ACE in the middle. While holding the cards with the faces up, you ask a volunteer to clip a paperclip on the ACE. That’s easy! Now you take the paperclip off and turn the cards face down, asking your volunteer do clip the ACE again. Everyone thinks the volunteer has clipped the ACE again, but when the cards are turned over, the volunteer wasn’t even close! This can be repeated a couple of more times and every time the volunteer is wrong!
The ACE card looks like it’s in the middle, but it’s really a bit off center. To paperclip the ACE when the cards are turned over (showing their backs), you need to put the paperclip on the left edge of the last card on the right (the card showing it’s full back). Try it yourself.