Although Manually Scheduled task mode sounds like heresy to hardcore project managers, it comes in handy in several situations. Scheduling activities like training classes with set dates is a snap with a manually scheduled task. And they’re great during planning, when you don’t know all the info about a task — fill in what you know and leave the rest blank, type TBD, or add a note about what you do know.
Perhaps, manually scheduled tasks’ finest moment comes during top-down planning. Suppose management has given you timeframes for a project: 12 weeks for design, 18 weeks for development, and6 weeks for testing. In Project 2010, you can create manually scheduled summary tasks and specify their duration. Then, as you create subtasks under those summary tasks, Project keeps track of the duration you specified for the summary task as well as the total duration of its summary tasks. You can see whether the subtasks fit within the summary task duration or run past the allotted time.
As shown in the screenshot, the black summary bar represents the summary task duration you entered. The red bar below it shows the duration of the subtasks. The red indicates that the subtasks take longer than the summary task duration. If the subtasks took less time, the bar would be blue. The length of the two summary task bars show you whether you have any buffer available.