Assign Symmetry Lines
In addition to the reference elements, the configuration of this part suggests that it would be useful to assign symmetry line constraints to the centerlines of the elements that we're going to be resizing.
1. Click Parametric and then, in the Create group, click 
Constraints.
Constraints.The Generate Constraints dialog box opens.
2. In the Action area, click Assign.
3. In the Type box, select Symmline.
4. Click Apply.
5. Click the four centerlines that run through the holes in the two views. Figure 241 shows the placement of these constraints.
6. Click 
OK.
OK.