If each element in the Routing Unit is listed individually, the number of columns to read will equal the number of elements in the Routing Unit. However, if there are several elements with consecutive numbers in a Routing Unit, they can be listed by specifying the first one in one column and the last one with a hyphen in front of it in the next column.

The ID of the Routing Unit is a primary key referenced by define in rout_unit.rtu. All IDs in the rout_unit.def file must be unique.

If elem_tot = 1, there can be only one element in the Routing Unit, whose ID (id in rout_unit.ele) is specified in this column. If elem_tot > 1, this column is followed by additional columns listing the elements included in the Routing Unit, but those columns will not have a header. If there are several elements with consecutive numbers in a Routing Unit, they can be listed by specifying the first one in one column and the last one with a hyphen in front of it in the next column.

The name of the Routing Unit is not used by the model.