If a task must start or finish on or near a specific date, just linking tasks and adding lead or lag time might not do the trick. This may be the time to set a constraint. The type of constraint you set for a task depends on the task’s scheduling requirements.
To set a constraint
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To check a constraint
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Microsoft Project replaces the fields in the Gantt Chart view, listing the task constraints. If necessary, scroll to see the fields.
Warning: Dragging in Constraints
If you create a task by dragging on the Gantt Chart or Calendar, Microsoft Project imposes a constraint
date on the task. A constraint is also applied if you drag a task bar to move a task on the Gantt Chart or
Calendar. Microsoft Project assumes that because you’re dragging a certain date, you’re indicating a start or
finish date for the task. The constraint imposed is Start No Earlier Than or Finish No Earlier Than, depending
on where you start and finish dragging. Microsoft Project imposes the same constraint types when you type a
start or finish date for a task.