Symmetric

This constraint forces two points to be symmetric about some plane. Conceptually, this means that if we placed a mirror at the symmetry plane, and looked at the reflection of point A, then it would appear to lie on top of point B.

The symmetry plane may be specified explicitly, by selecting a workplane. Or, the symmetry plane may be specified as a line in a workplane; the symmetry plane is then through that line, and normal to the workplane. Or, the symmetry plane may be omitted; in that case, it is inferred to be parallel to either the active workplane’s vertical axis or its horizontal axis. The horizontal or vertical axis is chosen, depending which is closer to the configuration in which the points were initially drawn.