Applies geometric constraints to a selection set of objects based on orientation of the objects relative to one another.
Access Methods
Button
Toolbar: Drafting tool set 
Parametric tool group Auto Constrain Menu:
Parametric
AutoConstrain
Summary
You can apply geometric constraints to a selection set of geometry within the specified tolerance set using the AutoConstrain tab in the Constraint Settings dialog box.
Specify the Settings option to change the types of constraints applied, the order in which they are applied, and the applicable tolerances.
The Settings option displays the Constraint Settings dialog box with the Autoconstrain tab selected.