Constraints are recognized real-world restrictions that affect project performance. Any factor that potentially delays when an activity can be scheduled is a constraint. The most typical constraints are date restrictions. Constraints can apply to the entire project or only to individual activities and can even reflect external project requirements that cannot be built into the network logic. Some examples of constraints are: must finish by (project-level constraint) and start on or after (activity-level constraint). You can apply up to two constraints to activities in the Status detail window of the Activities page, or by dragging the start or end of a bar in the Gantt view of the Activities page.