In the electrical sector, there are parts/semi-finished products whose geometry is not fixed in one spatial direction. These are in particular busbars, cable ducts and above all mounting rails ("DIN rails"). These parts are characterized by the fact that their geometry is defined by a certain two-dimensional profile and an "extrusion length" in the Z direction. Accordingly, such parts are modeled differently in various ECAD systems such as EPLAN. For this situation, a STEP file alone does not provide a particularly suitable representation.

The basic properties of such parts are described by the classes CNSELEK|10|1, CNSELEK|10|2 and CNSELEK|10|3. These classes all have a common attribute.