The 
Surface Boundaries Diagnostic tool is used to check that all surfaces in the model have correct and valid boundaries, both external and internal. The most common cause of errors is that the start of one curve does not match with the end of the next curve in a trimming loop. If problems are detected, check the model in your original CAD system and/or the parameters used to export the model.
To access this tool, import a geometry file, e.g. IGES (*.igs), STEP (*.stp, *.step), or Parasolid (*.x_t, *.x_b, etc.) using
> Import, and then select ().
Dialog elements
- Check outer boundaries
- Select this option if you want the diagnostic to search for surfaces where the external boundary does not form a closed loop.
- Check inner boundaries
- Select this option if you want the diagnostic to search for surfaces with an internal boundary that does not form a closed loop.