Most metal files are forged with a long spur at one end with no teeth cut into it. This is called a tang.
The tang is the part of the file that fits inside the handle. However, files with tangs are quite often sold without handles.
It is recommended that files should always be fitted with handles both for comfort and the prevention of injury.
Files with no tang are referred to as ‘plain’. These files are held by their body, in a similar way to an emery board.