The old style of filing correspondence was by alphabetical arrangement in flat files. These as they became full were stored with their contents. Unless the files were rearranged - which was a rare occurrence - they contained live as well as dead correspondence. For instance, when the file "Sa-So," was removed with its contents from the series, letters from the Smith Manufacturing Co. might be needed daily with no recourse except to either assort them and place them in the new file or refer to the stored file. Then, too, letters pertaining to and even coming directly from the Smith Mfg. Co. might be indexed under other letters and be overlooked when the firm's correspondence is assembled.
This system of filing letters, papers, circulars and similar matter is an improvement over flat sheet files, just as the card system is an improvement over books. It consists of a cabinet of drawers in which folders are placed on edge between guide or index cards. In the folders is placed the matter to be filed, there being one folder for each firm or subject.
If the folders are arranged numerically, which is advisable in almost every case, each firm or subject is given a number corresponding to the folder representing it. Guide cards with numbered projections to quickly catch the eye are placed at intervals of 10 or 20 and facilitate quick reference to any folder. In the best system, the cards bearing these numbers are arranged either alphabetically, geographically or topically as desired by the user.