1. TECHNICAL FIELD OF THE INVENTION;This invention relates to a steel ball used for storing documents in a holder.;2. The technical problem to be solved by the invention;The present invention is intended to provide a steel ball that prevents the departure from the holder, can be used conveniently, simplify the installation and reduce the economic cost.;3. Summary of solution of design;According to the present invention, a paper holder having a paper holder is formed, a pair of engaging pieces are formed at a predetermined interval in the center of the paper holder, and a protrusion is formed at a predetermined length in the center of the paper holder to prevent the holder from being detached from the holder. It is to prevent the deformation of the paper shelf when filing documents.;4. Significant Uses of the Invention.;It is to be used in holders for storing documents.
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