External HDD pockets

External

— pockets designed for use in the format of external peripherals, without installation inside the computer (laptop) case.

The purpose of such an accessory is to turn the internal drive into an external one. This can be convenient, for example, if the user has to periodically travel on business trips: for such a trip, you can remove the drive with working materials from the computer and take it with you, and put it back when you return. Another example is a working HDD or SSD left over from an old system and not needed inside a new computer: such a drive with an external pocket can be a good (and certainly cheaper) alternative to a new purely external device.

Note that docking stations (see the relevant paragraph) formally also refer to external pockets; however, such devices have their own specifics, which is why they are singled out in a separate category.