As part of your overall security plan, you can control whether other FileMaker Pro files are permitted to access the schema in a file (including its tables, layouts, scripts, and value lists) in your secured solution. When protection is enabled, any use of the protected file through a FileMaker data source will require authorization. Therefore, in a multi-file solution, you will need to authorize the other files.
For example, enabling protection prevents someone with an account in your file from creating another file that uses tables in your file but does not implement the same business logic (such as the same script triggers). The use of this alternative file can bypass your intended business logic (although record-level access would still be enforced). Turning on this option also prevents files that are not authorized from opening a protected file using the Open File script step.