Reverse the tangent direction of a curve (by swapping the start and end points), or the parametric directions (U/V) of a surface.
Reverse, swap, or examine the directions (tangents) of a surface
An indicator appears on the surface showing the current tangent(s) (U, V, or both, depending on the option chosen).
Reverse the direction of a curve
The tangent of the curve is shown at the point where you clicked.