Ring binders are large folders that contain file folders or hole punched papers. These are held in the binder by circular or D-shaped retainers, onto which the contents are threaded. The rings are usually spring-loaded, but can also be secured by lever arch mechanisms or other securing systems. The binders themselves are typically made from plastic, with metal rings. Early designs were patented during the early 1890s to the early 1900s.
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