Select to have interactive control. In many instances, the geometric parameter Beta, which is computed for cylindrical shell geometry, exceeds the parameter Gamma for certain WRC 107/537 curves. If this option is not selected, then the software uses the last point on the curve that is available and completes the analysis. If this option is selected, then the software pauses and ask you to enter what a value of the stress parameter from the WRC 107/537 curves. In most cases, this option is not selected.