I don't know how this works...but it does!

[ph1l]

I dunno, doesn't look like a rhombus from this angle...

View attachment 326958

That's the illusion. But measuring the angles shows one is about 78 degrees, and the other is about 102 degrees.

 

[Frederick Foresight]

It's because he's not putting the card through the hole. He's holding the card behind the piece of paper. It's called sleight of hand.

On second thought, you might be right.