diff --git a/libsrc/occ/occ_utils.cpp b/libsrc/occ/occ_utils.cpp
index 8b747137..210e358e 100644
--- a/libsrc/occ/occ_utils.cpp
+++ b/libsrc/occ/occ_utils.cpp
@@ -11,6 +11,22 @@ namespace netgen
         return occ2ng( Handle(BRep_TVertex)::DownCast(shape)->Pnt() );
     }
 
+    Transformation<3> occ2ng (const gp_Trsf & occ_trafo)
+    {
+        Transformation<3> trafo;
+        auto v = occ_trafo.TranslationPart();
+        auto m = occ_trafo.VectorialPart();
+        auto & tv = trafo.GetVector();
+        auto & tm = trafo.GetMatrix();
+        for(auto i : Range(3))
+        {
+            tv[i] = v.Coord(i+1);
+            for(auto k : Range(3))
+                tm(i,k) = m(i+1,k+1);
+        }
+        return trafo;
+    }
+
     Box<3> GetBoundingBox( const TopoDS_Shape & shape )
     {
         Bnd_Box bb;
diff --git a/libsrc/occ/occ_utils.hpp b/libsrc/occ/occ_utils.hpp
index 1e9fa9a1..e51a2b51 100644
--- a/libsrc/occ/occ_utils.hpp
+++ b/libsrc/occ/occ_utils.hpp
@@ -9,6 +9,7 @@
 #include <TopTools_IndexedMapOfShape.hxx>
 #include <TopoDS.hxx>
 #include <TopoDS_Vertex.hxx>
+#include <gp_Trsf.hxx>
 
 #include "meshing.hpp"
 
@@ -47,6 +48,8 @@ namespace netgen
         return occ2ng (BRep_Tool::Pnt (v));
     }
 
+    DLL_HEADER Transformation<3> occ2ng (const gp_Trsf & t);
+
     inline gp_Pnt ng2occ (const Point<3> & p)
     {
         return gp_Pnt(p(0), p(1), p(2));
diff --git a/libsrc/occ/occgeom.cpp b/libsrc/occ/occgeom.cpp
index 290c4ece..b013b073 100644
--- a/libsrc/occ/occgeom.cpp
+++ b/libsrc/occ/occgeom.cpp
@@ -1940,12 +1940,19 @@ namespace netgen
       return occ2ng( props.CentreOfMass() );
   }
 
-  void OCCGeometry :: IdentifyEdges(const TopoDS_Shape & me, const TopoDS_Shape & you, string name, Identifications::ID_TYPE type) 
+  void OCCGeometry :: IdentifyEdges(const TopoDS_Shape & me, const TopoDS_Shape & you, string name, Identifications::ID_TYPE type, std::optional<gp_Trsf> opt_trafo) 
   {
-    auto cme = GetCenter(me);
-    auto cyou = GetCenter(you);
-    Transformation<3> trafo{cyou-cme};
-    identifications[me.TShape()].push_back( {me.TShape(), you.TShape(), Transformation<3>(cyou - cme), name, type} );
+    Transformation<3> trafo;
+    if(opt_trafo)
+        trafo = occ2ng(*opt_trafo);
+    else
+    {
+        auto cme = GetCenter(me);
+        auto cyou = GetCenter(you);
+        trafo = Transformation<3>{cyou-cme};
+    }
+
+    identifications[me.TShape()].push_back( {me.TShape(), you.TShape(), trafo, name, type} );
 
     auto vme = GetVertices(me);
     auto vyou = GetVertices(you);
@@ -1976,6 +1983,11 @@ namespace netgen
       std::map<T_Shape, T_Shape> vmap;
 
       auto verts_me = GetVertices(me);
+      auto verts_you = GetVertices(you);
+
+      if(verts_me.size() != verts_you.size())
+          return false;
+
       for (auto i : Range(verts_me.size()))
       {
           auto s = verts_me[i].TShape();
@@ -1987,7 +1999,7 @@ namespace netgen
       }
           
       bool all_verts_mapped = true;
-      for (auto vert : GetVertices(you))
+      for (auto vert : verts_you)
       {
           auto s = vert.TShape();
           auto p = occ2ng(s);
@@ -2006,22 +2018,40 @@ namespace netgen
       return all_verts_mapped;
   }
 
-  void OCCGeometry :: IdentifyFaces(const TopoDS_Shape & solid, const TopoDS_Shape & me, const TopoDS_Shape & you, string name, Identifications::ID_TYPE type) 
+  void OCCGeometry :: IdentifyFaces(const TopoDS_Shape & solid, const TopoDS_Shape & me, const TopoDS_Shape & you, string name, Identifications::ID_TYPE type, std::optional<gp_Trsf> opt_trafo) 
   {
-    auto cme = GetCenter(me);
-    auto cyou = GetCenter(you);
-    Transformation<3> trafo(cyou-cme);
+    Transformation<3> trafo;
+    if(opt_trafo)
+    {
+        trafo = occ2ng(*opt_trafo);
+    }
+    else
+    {
+        auto cme = GetCenter(me);
+        auto cyou = GetCenter(you);
+        trafo = Transformation<3>(cyou-cme);
+    }
 
-    identifications[me.TShape()].push_back
-        (OCCIdentification { me.TShape(), you.TShape(), trafo, name, type });
+    auto faces_me = GetFaces(me);
+    auto faces_you = GetFaces(you);
 
-    auto edges_me = GetEdges(me);
-    auto edges_you = GetEdges(you);
+    for(auto face_me : faces_me)
+        for(auto face_you : faces_you)
+        {
+            if(!IsMappedShape(trafo, face_me, face_you))
+                continue;
 
-    for (auto e_me : edges_me)
-      for (auto e_you : edges_you)
-        if(IsMappedShape(trafo, e_me, e_you))
-            IdentifyEdges(e_me, e_you, name, type);
+            identifications[face_me.TShape()].push_back
+                (OCCIdentification { face_me.TShape(), face_you.TShape(), trafo, name, type });
+
+            auto edges_me = GetEdges(me);
+            auto edges_you = GetEdges(you);
+
+            for (auto e_me : edges_me)
+                for (auto e_you : edges_you)
+                    if(IsMappedShape(trafo, e_me, e_you))
+                        IdentifyEdges(e_me, e_you, name, type, opt_trafo);
+        }
   }
 
   void OCCParameters :: Print(ostream & ost) const
diff --git a/libsrc/occ/occgeom.hpp b/libsrc/occ/occgeom.hpp
index 27eae5b7..790d9727 100644
--- a/libsrc/occ/occgeom.hpp
+++ b/libsrc/occ/occgeom.hpp
@@ -341,8 +341,8 @@ namespace netgen
     bool ErrorInSurfaceMeshing ();
 
     //      void WriteOCC_STL(char * filename);
-    static void IdentifyEdges(const TopoDS_Shape & me, const TopoDS_Shape & you, string name, Identifications::ID_TYPE type);
-    static void IdentifyFaces(const TopoDS_Shape & solid,const TopoDS_Shape & me, const TopoDS_Shape & you, string name, Identifications::ID_TYPE type);
+    static void IdentifyEdges(const TopoDS_Shape & me, const TopoDS_Shape & you, string name, Identifications::ID_TYPE type, std::optional<gp_Trsf> opt_trafo = nullopt);
+    static void IdentifyFaces(const TopoDS_Shape & solid,const TopoDS_Shape & me, const TopoDS_Shape & you, string name, Identifications::ID_TYPE type, std::optional<gp_Trsf> opt_trafo = nullopt);
 
   private:
     //bool FastProject (int surfi, Point<3> & ap, double& u, double& v) const;
diff --git a/libsrc/occ/python_occ_shapes.cpp b/libsrc/occ/python_occ_shapes.cpp
index e52d270b..bf4d90ab 100644
--- a/libsrc/occ/python_occ_shapes.cpp
+++ b/libsrc/occ/python_occ_shapes.cpp
@@ -1091,7 +1091,7 @@ DLL_HEADER void ExportNgOCCShapes(py::module &m)
       }, py::arg("other"), py::arg("name"), py::arg("type")=Identifications::PERIODIC, "Identify shapes for periodic meshing")
 
     .def("Identify", OCCGeometry::IdentifyFaces, "Identify faces",
-            py::arg("from"), py::arg("to"), py::arg("name"), py::arg("type")=Identifications::PERIODIC)
+            py::arg("from"), py::arg("to"), py::arg("name"), py::arg("type")=Identifications::PERIODIC, py::arg("trafo")=nullopt)
 
     .def("Distance", [](const TopoDS_Shape& self,
                         const TopoDS_Shape& other)