/                                                           Trapez

                                                        ­                      
                                          ­                                   ist

                                                            ­   move



                                                         ­                 s*

                                                             along

                                                          ­     t
                                                               ­       
                                                     h

                                                              ­            e

                                            
                                                           i       n      
                                                         ­   
                                                             v 

     
                                                       ­               i

            
                                  ­                                si


                            ­                                         b  
                                                                ­       le


                                                       Thread