Curve Length Constraint
Set a constraint to the length of a spline, if the end points of the spline are fixed. You can edit the shape of the spline by modifying the curve length value.
Add a Curve length constraint to a spline in a plane sketch or in a 3D sketch.

- Select the spline curve.
 - Select the context-sensitive menu function Constraints> Curve length.
The added length constraint is displayed only in the feature tree of the part.
 
Note: 
  - In a 3D sketch, you can use this constraint in modeling hoses, for example. The Piping Design hose parts use this technique.
 - You can edit the constraint using the functions in the feature tree of the part. Select the dimension constraint and the context-sensitive function Edit, or double-click the dimension constraint.
 
