001 Joiner and Splitter Pro allows you to join and split files of any size and type. The files created have the extensions of *.001,*.002,*.003, etc. All you have to do is double click the .001 file and the rest will be joined together instantly! We proudly introduce 001 Joiner and Splitter Pro. 001 Joiner and Splitter Pro allows you to join and split files of any size and type. The files created have the extensions of *.001,*.002,*.003, etc. An example file might be something like Myfile.avi.001 and Myfile.avi.002, etc. All you have to do is double click the file with extension .001 and the rest will be loaded into 001 Joiner and Splitter Pro and will be joined together with more click of your mouse. Give it a try today!