Solutions: Public vs Private

The individual solutions articles should be able to be made either 'public' or 'private' within a folder. For instance, I have a folder under Software category called Adobe. There are articles for end users to self-help, but there are also articles for agents to use for reference when helping. We shouldn't have to create another folder structure for the private, agent-only articles. Just need a checkbox and a field that marks each article as either private or public, that's all.