You can add geometric objects, such as wireframe lines or curves, to mesh models. This is useful if you want to add triangles to fill a hole or gap in a mesh, as you can select points on the object to use as nodes.
For example:
For example, you may add a line to help bridge the gap in the mesh, as shown below:

and
, which are existing vertices:
, the mid-point of the line, to create the final node.The new triangle is drawn:
