To me, an absolutely useless piece of software. Let me tell you what my experience is.
Starting the app, clicking on Concat, indicating one of the two files (filename.sitx.001 and .filename.sitx.002), split by someone else, with the same tool. Indicating output folder, clicking on Choose...
The result:
'You are trying to do something strange, like splitting a folder or disk. Place a folder or disk on a disk image first!'
What? :) And this work receives 3.5 stars? What for?
Anyway, it may work for someone else, but the way it is explained in the help file, does not.
Does not do the job, useless.