AJoiner is a lightweight tool that can join segments of data, restoring the original file(s) after processing it with a splitter. The application has a very simple layout which makes it easy to use. AJoiner only works with Mastersplitter's type of extensions and is distributed as freeware.
With this tool you only need to load the file segments; the joining dialog will be immediately triggered. The program's strength lies in the fact that it's quite small for its capabilities (less than 200 KB). It can process multiple join tasks in either simultaneous or consecutive manner. Users can even choose the application's behavior when encountering missing files: cancel if a specific number or percentage of files are missing. However, AJoiner works with just Mastersplitter type of file formats (*.001-*.999); the program is unable to recognize output formats that are created using other splitting applications.
On the whole, if all you are looking is a lightweight tool for joining files, AJoiner should do the job. Otherwise, there are better free joiners out there that can also split files.