8.5 x 11 inch paper
list of examples of two different categories of items
To make a sorting folder, just fold a piece of paper in half "hot dog style", then open the fold and fold up about a third of the way to make a pocket for the cards.
Then print a list of examples for each category and cut them apart. The students are to sort the set into the two categories. I ask students to work in teams of two when using their sorting folders. Its great review before a test or before the final exam at the end of the course.
My examples are for chemistry, but sorting folders can be designed for any subject where you are sorting between categories, or even as a series of examples and non-examples.