This one really had me baffled, so I had to open it up. I slit it open along one edge.
The yellow arrows are what I slit apart.
The orange arrow is an “island” piece of cardboard attached between the sides.
The red arrow is a very fine plastic ribbon that loops around the “island,” attached to each of the sliding parts. So when you pull one one way, the other goes the other way.
Seems like a magic trick. Clever!
