Lets you adjust the user-defined normal of a vertex (or several selected vertices) using a manipulator. For example, you can make sharp edges appear smoother or adjust the lighting on a polygonal object by modifying the direction of the vertex normal.
Editing the vertex normal with this tool overrides the existing Maya normals for the mesh and locks the user-defined normal you set. You can unlock the user-defined normal using the Normals > Unlock Normals feature.
Editing normals with face/vertex components can cause new hard edges, any unlocked neighboring normals might move in the process. Lock any neighboring normals you want to remain unaffected prior to editing.
