Chef and Ridges

We have a rectangular piece of cardboard with width $1$ (its height is not important). We are going to fold it in the following way: - pick up the right side of the piece of cardboard and move it to the left until it touches the left side - this way, a smaller piece of cardboard with width $1/2$ is created; if we unfolded it, we could see a vertical ridge formed in the middle - pick up the left si