1. A method for constraining a graphical model in a computer-aided design (CAD) system, comprising: receiving a graphic model in a CAD system; receiving a selection of a symmetric constraint by the CAD system; receiving a selection of a first curve of the graphic model by the CAD system, the selection indicating a first point at a location on the first curve; receiving a selection of a second curve of the graphic model by the CAD system, the selection indicating a second point at a location on the second curve; determining a user's intent by the CAD system based on the locations of the first point and the second point, including designating at least one vertex of the first curve according to the location of the first point and designating at least one vertex of the second curve according to the location of the second point; applying a symmetric constraint between the first and second curves, by the CAD system, according to the user's intent and the designated vertices; and storing and displaying graphic model by the CAD system.