Typically you'll lock down access to a SQL Reporting Services Model by creating a Perspective, either for security or to limit the amount of attributes available for a report. By default, the main model will be available in Report Builder with children listed for your available Perspectives.But Report Builder is meant for ad-hoc generation by non-technical users. They might click the parent model instead of a perspective since it's the first entity they see on the screen or since they just don't know any better.To help guide those users and to enforce the use of a Perspective you can disable the ability to build reports from the main model.