Was looking at the database definition of the contact management template included with FM 8.5 and above. Could someone tell me why there are fields like "Scratch", Similars CompanyKey, Similars Multikey ans so on. What purpose do these fields serve?

Thanks in advance for any pointers to any resources on the web or books explaining the design of built-in templates in filemaker.

A lot of the FileMaker example files have these "similars" fields, with relationships and portals. It is so you could see other people or companies which have the same name (or whatever). In my opinion, and no offense to the author, while demonstrating some useful methods, such as self-relationships and a possible way to try and avoid duplicates, they are not all that essential, especially if you highly value screen space and a compact Relationship Graph. Unless you want them, I'd say you're safe to remove them. They have little to do with the main functionality of the files.

Scratch is generally a global field, used to temporarily hold various data. It is their idea of reusing a global field I imagine. It is used by something, so I would not delete it.

I doubt there is any real documentation of the templates. You are wise to question them, as they are not always "up-to-date" with the latest most efficient techniques.