Sets the multiplicity of the selected CVs.
By default, when you create a cubic curve, the end knots have a multiplicity factor of 3 and the arcs in between have a multiplicity factor of 1.
Full changes the multiplicity of the interior CVs from 1 to 3. To change a multiplicity factor from 1 to 3, there must be at least two CVs on each side of the CV being modified that have a multiplicity factor of 1.
Off changes the multiplicity of the interior CVs from 3 to 1.
If you turned on Keep Original when you adjusted CV hardness, you can use the Attribute Editor to edit the CV hardness any time later. See also hardenPoint.