Layout > Working with Entities > About Using Constraints
  
About Using Constraints
Use constraints to apply design intent to geometric or construction entities in a layout at any time during the design process. You can convert any of the guide relationships, as well as coincident point and midpoint geometry, into constraints. In Constraint mode, you can convert guide references into constraints and vice versa.
Keep in mind the following points when using constraints in a layout:
When you create geometry, constraints are automatically offered and the relevant geometry is highlighted.
Constraints automatically display when you mouse over or select geometry with constraints.
Best practice is to limit the number of constraints that you apply. A large number of constraints can impact performance.
You can set the layout_smart_constraints configuration option to automatically create constraints when creating geometry, such as fillets with tangent arcs.