Meaning: The evaluation of the opening or slab root outline geometry failed because it is not planar (defined in the support plane). Recovery: Check the selected boundaries. For a slab: Open the Structure task. Click Select . Set the Locate Filter to Slabs. Select the slab. Select Define Boundaries on the ribbon. Redefine the boundaries of the slab. Click Finish. For an opening: Open the Structure task. Click Select . Set the Locate Filter to Openings. Select the opening. Select Boundary on the ribbon. Redefine the boundaries of the opening. Click Finish.