Adaptive Release gives you the ability to restrict access to a content item (e.g. Assignment, File, URL, Item, Folder) to selected students / group of students, only show item if a certain grade has been achieved in an assignment or limit it by date.

Please note that you should check that the user that you want to restrict access to is already enrolled on the course since Blackboard will allow you to add any user in the system in the membership category even if they are not currently enrolled on the course.

Click here to view a video about setting up Adaptive Release rules.

More detailed information about Adaptive Release is available here.