To Adjust Feature Top
The Adjust Feature Top element appears only for No Stock machining, that is, for NC models with no stock defined. For such models, you have to supply a value for the thickness of material to be removed.
1. In the machining feature dialog box (for example, Profile Feature), click 
next to the Adjust Feature Top element.
next to the Adjust Feature Top element.The system opens the Define/Adjust Feature Top dialog box.
2. Use the following options in the Define/Adjust Feature Top dialog box:
◦ Offset above floor—Type a value of material thickness from the feature Floor. This option is available only for features with a Hard Floor, such as Pocket or Step.
◦ Offset above walls—This option is available only for Through features, such as Profile, Through Pocket, or Through Slot. By default, the offset value is 0; that is, the feature top coincides with the top of the feature Hard Walls. You can type a different offset value, to extend the feature above the top boundary of the Hard Walls.
◦ Use Datum Plane—Select or create a datum plane normal to the z-axis of the Program Zero coordinate system.
◦ Offset from Program Zero—Type a value along the z-axis of the Program Zero coordinate system.
3. Click Preview to display the currently defined feature top in cyan.
4. Click OK to return to the machining feature dialog box.