• Ref. Geometry >> Create >> Plane >> Tangent Plane command adds a reference plane tangent to a selected polygon mesh at a point.

Step   

Execute Ref. Geometry >> Create >> Plane >> Tangent Plane command as follows:

1. Select the faces to which the reference plane is tangent, or skip this step.

2. Select Ref. Geometry >> Create >> Plane >> Tangent Plane from the menu or click the corresponding icon from the Reference toolbar.

3. Select a point on a shell that the reference plane passes through.

If step 1 is skipped, the following dialog box appears.

Check Use Average Normal of Neighboring Vertices option to use the average normal of neighboring vertices of a selected point as the normal of the to-be-generated reference plane.
Or press OK button without checking this option to use the normal of the polygon mesh on which the selected point is placed.