This is used to convert MSBuild project files created using the example GUI supplied with Sandcastle to the help file builder project file format.
The example GUI project files are quite simple and only contain a few options that convert straight across to the equivalent help file builder project properties. After conversion, review the Documentation Sources and References project nodes to see that the required items were imported correctly and make any necessary adjustments.
Given that solutions and projects are supported as documentation sources, you may find it easier to add them as documentation sources instead of the assemblies, comments, and references that they contain. When a solution or project is used, these items are imported from them automatically at build time.