diff --git a/EGkSurfFlatRegion.h b/EGkSurfFlatRegion.h
index bb11f61..6a1d2be 100644
--- a/EGkSurfFlatRegion.h
+++ b/EGkSurfFlatRegion.h
@@ -32,6 +32,7 @@ class __declspec( novtable) ISurfFlatRegion : public ISurf
       virtual bool AddExtLoop( ICurve* pCrv) = 0 ;
       virtual bool AddIntLoop( const ICurve& cCrv) = 0 ;
       virtual bool AddIntLoop( ICurve* pCrv) = 0 ;
+      virtual bool Cut( const Plane3d& plPlane) = 0 ;
       virtual bool Add( const ISurfFlatRegion& Other) = 0 ;
       virtual bool Subtract( const ISurfFlatRegion& Other) = 0 ;
       virtual bool Intersect( const ISurfFlatRegion& Other) = 0 ;