Classic® folders and covers are bound / lined binders, in which the core is bookbinder card board in the correct thickness.
Often bound with a lined printed matter, in matte or blank protetive foil, but there are countless other options such as canvas of cotton or synthetic material, leatherette (or genuine leather) or specially developed paper qualities with high durability. The possibilities are endless.
The folders and covers are equipped with a closing mechanism and handle. It can be an elastic and a button, or a clasp on a schoolbag with mounting of different handles of various types and material.
Covers for menus has an elastic to secure menus, but the solution can also be more advanced.