Jettisons vertices that are not part of the final triangulation from the output .node file. By default, Triangle copies all vertices in the input .node file to the output .node file, in the same order, so their indices do not change. The -j switch prevents duplicated input vertices, or vertices `eaten' by holes, from appearing in the output .node file. Thus, if two input vertices have exactly the same coordinates, only the first appears in the output. If any vertices are jettisoned, the vertex numbering in the output .node file differs from that of the input .node file.