Sketcher > Dimensioning Sketcher Geometry > To Add Relations to a Section
  
To Add Relations to a Section
You can add relations to sections while you are in Sketcher mode. Relations in Sketcher mode follow the same rules as in Part mode, except the parameters must belong to a model and cannot be created in Sketcher mode. The relations apply to the section, but you can modify and use them in part or assembly relations.
You can also enter a section relation when you modify the driven dimension. Enter the relation (for example, sd4=sd2+sd3/2) when you are modifying dimension values. The new relation is displayed and you are prompted to accept it.
When you add the relation, use dimension symbols as follows: sd# for normal Sketcher dimensions, rsd# for reference Sketcher dimensions, and kd# for known dimensions.
 
* Only Sketcher, reference, and known dimensions are allowed in relations created within Sketcher mode.