From Chapter 2, Input File Creation you know that there are two types of edges, i.e. Dirichlet and Neumann edges. So it is essential that you specify this for each and every edge in the drawing. In this mode, you will be able to left-click on any edge and edit its type. Once you left click, you will see a dialog window like Figure 3.5, “Editing Lines Dialog”. Then you just have to select its type. We should note that all edges are assumed to be of type Neumann, unless specified otherwise.