The optional turnedSecondCurve attribute shows if the second curve is inverted. A value of 1 (or true) means the second curve is inverted. A value of 0 (or false) means the second curve is not inverted.
Source
<xs:element name="Ruled23Core" type="Ruled23CoreType" substitutionGroup="SurfaceCore"><xs:annotation><xs:documentation>The global Ruled23Core element is the mathematical core of a ruled surface.</xs:documentation></xs:annotation></xs:element>