A binary contents file is intended for large Microsoft HTML Help projects. It reduces the amount of time it takes to open topics from the Contents tab.
WARNING! Do not use external TOC files with a binary contents file because your table of contents will not work properly.
Use the TOC Composer and create the table of contents for your project.
From the File menu, select Project Settings.
Click the TOC Styles tab.
Select Binary TOC. The remaining options at this dialog are unavailable with binary contents files.
Click OK to save the settings.
Compile the project.