Hudson can record the 'fingerprint' of files (most often jar files) to keep track of where/when those files are produced and used. When you have inter-dependent projects on Hudson, this allows you to quickly find out answers to questions like:

- I have `foo.jar` on my HDD but which build number of FOO did it come from?
- My BAR project depends on `foo.jar` from the FOO project.

- Which build of `foo.jar` is used in BAR #51?
- Which build of BAR contains my bug fix to `foo.jar` #32?

To use this feature, all of the involved projects (not just the project in which a file is produced, but also the projects in which the file is used) need to use this and record fingerprints.

See this document for more details.