When moving points on a power surface, you can use the N keyboard key to lock the axis to guarantee the point is being moved in a perpendicular direction from the surface. The locked axis is the original point's surface normal.
When you use the N key, the drag point is locked on the axis, normal to the surface from where you picked the original point.
Note: This does not work if you are using a view that looks down the surface normal. Change views to see the point moving perpendicular to the surface.
In these examples, both corner points on the surfaces have been dragged to change their shape from a standard plane. The N keyboard key was used for the image on the right to move the surface in a perpendicular direction to the surface normal.
The effect is not visible until the surfaces are rotated, seen in the following rotated examples.
