This is a template attribute. Template attributes can be used in filtering, or to retrieve data from the model to use in drawings and reports. For example, when you create a report, Tekla Structures replaces the attributes added in the report template with the corresponding object property values.
The position number of parts. Shows a blank cell for all other objects.
Shows the mark of assembly main part for assemblies, parts, and bolts. For all other objects the field is blank.