A constraint is a logical relationship between entities in a sketch. Constraints control Sketcher geometry by removing degrees of freedom from the sketch. The various constraint types are described in “Using constraints to control sketch geometry,” Section 20.7.1. To change constrained geometry, you must either work within the defined constraints or modify the constraints to accept your changes. You can also constrain a sketch automatically using the Auto-Constrain tool. For more information, see “Automatically constraining a sketch,” Section 20.12.1.
To add a constraint:
From the tools in the Sketcher toolbox, select the constraint tool 
. For a diagram of the tools in the Sketcher toolbox, see “The Sketcher tools,” Section 20.4.1.
Abaqus/CAE opens the Add Constraint dialog box.
Select the type of constraint that you want to add to the sketch, and click Apply.
Abaqus/CAE displays prompts in the prompt area to guide you through the procedure.
Select the entity or entities to create the constraint.
Abaqus/CAE creates the constraint and displays the appropriate constraint symbol on the sketch. Sketch modification tools such as translate, rotate, scale, and mirror can override constraints.
To create additional constraints, repeat the above steps beginning with Step 2.
When you have finished creating constraints, click Cancel to close the Add Constraint dialog box.
