When Build starts, it checks out the project's .mdd file, if there is one, as this file will need to be updated with any changes that the user makes. It also checks out any image and template files in the project folder. If you want Build to check out any other files, add their extension names to the list defined for the CheckoutExtensionList key. Extensions in the list are separated with semicolons. The following statement shows the default setting for this key: