In the Start Flute area, select an option from the list to specify the profile of the start flute, then enter a value for the length of the flute:
- None — The tool plunges straight into the material.
- Linear — The profile is a straight line from the start depth
to the finish depth 
. 
- Curve — The profile curves from the start depth to the finish depth .
- Custom curve — Either drag the blue handles to determine the shape of the curve, or enter specific values for the top and bottom angles in the appropriate boxes.
- Length — Enter a value to determine the length of the flute. You can enter the value as a percentage or as millimetres. If you enter a percentage of 20, for example, the length of the flute is 20% of the length of the vector.