There are two principal types of filing systems found in modern offices
Vertical filing is the most common and is normally associated with filing cabinets. The files hang vertically with the identification tab on the top edge. Papers are added or retrieved from the top. As this type of filing is used in drawers or filing frames which pull out it has the benefit to the user in being easier to operate at lower levels. It is also easier to add new filing within an alphabetical system.
Lateral filing is when papers are added from the side of the file and the identification tab is on the side of the file. The main benefit of this type of filing system is that it is more space efficient. Lateral filing does not rely on drawers and a typical two metre high filing cupboard can house 6 rows of filing, double that of suspended filing. In addition as there are no drawers to pull out then there is less space used when standing at the cabinet or cupboard. When examining speed of filing and retrieval the lateral system is better, files tend to remain in a semi permanent location and therefore in the memory.  Again as there is no drawer filing and retrieval is a quick single handed action.
Add in new files in random positions can be an obstacle as the file is sometimes difficult to move along the rail.The TUB or coat hangar file can alleviate this