Jigsaw Download, or jigdo, is an intelligent tool that can be used on
the pieces of any chopped-up big file to create a special template file
that makes reassembly of the file very easy for users who only have the
pieces. What makes jigdo special is that there are no restrictions on
what offsets or sizes the individual pieces have in the original big
image. This makes the program very well suited for distributing CD or
DVD images (or large zip or tar archives) because you can put the files
of the CD on an FTP server--when jigdo is presented the files along
with the template you generated, it is able to recreate the CD image.