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.

CONCRETE_COVER_START shows the concrete cover thickness at the first end of the reinforcing bar. CONCRETE_COVER_END shows the concrete cover thickness at the second end of the reinforcing bar.

These are the values entered in the Start and End boxes in the Single rebar or Rebar group properties when the Cover thickness option is selected.