The Surface control tab is active for isoline milling or Z-level finishing.
On this page you can change the side of the surface that is milled. All
surfaces are listed as a row in the table. If the row has a check next
to it, the surface is included in the current operation. Uncheck it to
remove the surface from the operation. If you select a row in the table,
the surface is highlighted in the graphics window. Use the pick surface
button 
on the right to select a surface graphically and
select the appropriate row in the table. FeatureCAM attempts to mill the
correct side of each surface. The Machining Side column will be set to
Auto to indicate this. When a
surface is selected two arrows are displayed as shown in this figure.
The side with the arrow facing up will be machined. If the wrong side
is selected, click the Switch Machining Side 
button until
the arrow faces the proper way.
Isoline milling only
The order that the surfaces appear is the order that the surfaces will
be milled. The Up and Down arrows on the right side will move the operations
accordingly. When a surface is selected in the table, an arrow indicating
the starting corner and isoline direction is displayed along the surface
normal direction as show in this figure. The Start Curve column indicates
the current location. If you want to change the corner and direction of
the isoline paths, click the Set Isoline Row Column 
button
until the arrows face the proper direction.
Flowline Guide Surface
If you select a flowline guide surface the isolines of another surface are projected onto all the surfaces of the feature. See Flowline guide for more information.