With HJSplit you can not only split files, but also join the split parts back together again.
Information: A collection of split parts is set of files having all the same filename, except for the extension at the end of the file name (.001, .002, .003, etc.) . Combining/joining these split parts is equivalent to restoring the original (pre-split) file.
After clicking on the 'Join' button in the main HJSplit screen, you will see the following screen:
To join a set of files, just perform the steps indicated below.
(1) Make sure the set of split parts (set of files ending in .001, .002, .003, etc.) to be joined all reside inside the same directory.