To Recognize Symmetry
1. Click > 
Symmetry Recognition. The Symmetry Recognition tab opens.
Symmetry Recognition. The Symmetry Recognition tab opens. | You could also select a reference first, and then click Symmetry Recognition. |
2. Select either Identical or Similar to define a Symmetry Recognition feature with geometry that is either identical or similar to the seed surface.
3. Click the References tab, click the Seeds / Seed & Symmetry Plane collector, and select references by performing one of the following actions:
◦ Select one seed surface or surface region, and select one datum plane to serve as the plane of symmetry. The surface or region must be within the solid geometry or within the same quilt.
◦ Select two seed surfaces or surface regions that are symmetrically identical or similar. The two surfaces or regions must belong to the solid geometry, a single quilt, or two quilts.
▪ If you select one surface or surface region that is planar and one that is not planar, the planar surface or region is assumed to be the symmetry plane.
▪ If you select two planar surfaces or surface regions, both are assumed to be seed surfaces, and neither is assumed to be the symmetry plane.
4. To add curves and datums to the Symmetry Recognition feature, click the Curves and Datums (1st Seed) collector and select curves and datums. If two seed surfaces are selected in the Seeds / Seed & Symmetry Plane collector, the curve chains must be associated with the first surface or surface region listed in the collector. For curves, the entire curve chain must be selected.
5. Click 
OK.
OK.◦ If you selected one seed surface or surface region and one symmetry plane, then symmetrical surfaces are identified along with surfaces or surface regions that are connected to the seed surface.
◦ If you selected two seed surfaces or surface regions, then a symmetry plane is identified. The surfaces or surface regions connected to the selected seed surfaces that are symmetric in relation to the symmetry plane are also identified as part of the feature.