Generate -spring2 springs for nodes which have the same position in space. This can be used to connect these nodes with spring elements. Only nodes located on the specified geometry entity will be used.
The generated springs will get an element_group record with value element_group. So in that element group you can put the properties of the springs (see group_spring_stiffness etc.).
Typically you can use this option to connect meshes which were generated with different control_mesh_macro records or so.