Complex sentence: Duotangs are paper folders made of harder cardstock paper with flat metal teeth that people use to bind multiple sheets of paper simply by bending the metal teeth through the holes of the paper and folding them down to keep them in place.
Split into simpler sentences: Duotangs are paper folders made of harder cardstock paper with flat metal teeth. They are used to bind multiple sheets of paper by bending the metal teeth through the holes of the paper and folding them down to keep them in place.