Controlling sketch geometry helps you prevent unintended changes
by creating relationships between sketch entities. If all the geometry in a
sketch is controlled, the sketch is fully constrained—the entities in the
sketch cannot be modified without violating the controls, and you cannot add
another control without creating a conflict with one that already exists.
The following section describes how you can use constraints, dimensions,
and parameters to control sketch geometry. All three types of controls can be
considered constraints since they all work to restrict the degrees of freedom
in a sketch, but each control creates a different type of relationship between
the selected entities.