Iso-angle projects onto the surfaces from a certain angle, and creates shaded bands and/or lines where the surface is at right angles to the projection direction.
Create iso-angle display shading/lines
in the Diagnostic Shade window. To remove the shading and view the curves only, select Show Curves Only.
If the manipulator is not visible, click the Show Manip button.
It is often helpful to use multiple bands as you position the manipulator to give you more feedback, then switch to fewer or a single band.