Fillet
The Fillet constraint can be assigned to any arc that qualifies as a fillet in the model. To qualify as a fillet, an arc must have at least one line segment or arc element at each of its ends. When an arc is constrained to be a fillet, Solve will ensure that it remains tangent to both the elements at its endpoints. The fillet may change radius, length or orientation as a result of the solve.
To assign Fillet constraints:
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 Fillet.
4. Click Apply.
5. Click the arc to be constrained.
6. Click an element at each end of the arc to complete the fillet.
7. Click 
OK or assign the next constraint.
OK or assign the next constraint.Fillet-constrained arcs are represented by the fillet icon, .