box file

n.A container designed to hold flat, loose documents and to be stored vertically on a shelf, like a book.

Notes

Box files often contain dividers for organizing the documents and a spring clip to keep the contents from slumping. The effect was not unlike a book, with the back of the box visible on a shelf similar to a book binding and the top hinged to open like the front cover of a book. Box files were common in the 19th and early 20th centuries.