All you need to do is open the SF source code project and build it in debug mode. This will automatically place the debug DLLs in the GAC for you which will make them "debuggable" in all of your assemblies that reference the SF DLLs. If you'll recall, you can step into code several different ways. You can open the original SF code file or...if you are calling an SF class property or method, just step into it and it will automatically bring that source file up for debugging. Last, if you get an exception, it will automatically open the source file and show the line in error.