Tools
InfoAnalysisNormals
The Normals command under Analysis displays the normals to one or more surfaces, meshes (or solid faces) orcurves. You can always change the number of points where the normals are to be displayed and change their length.
Inspecting the normals may be useful when calculating the volume enclosed by one or more surfaces. In order to correctly calculate the volume, the normals of those surfaces must all face outwards.