I want to use the scale tool to move the selected vertices closer to each other, but I want to do so without affecting the shape of the face. The normals of the two face may not be the same either (they might point in reflected directions, i.e. one measures 30 degrees and the other -30 degrees).
In 3ds max you can enable face constraints, and then all vertex movements happen only along a face. Is there such a thing in Blender? Or is there another way to achieve this.