Apple Final Cut Pro 7 - Manual (Page 1243)

3 Move the pointer to the Canvas (the pointer turns into a crosshair pointer), then click to
change the location of the matte corner defined by Point 1.
Before changing the location
of the first point After changing the location
of the first point
4 Repeat steps 2 and 3 for the Point 2, Point 3, and Point 4 point controls, until you’ve
created a box that crops out everything outside the green screen surrounding the actor.
5 To round the four corners of the matte, adjust the Smooth slider, if necessary.
The matte, with rounded
corners
6 If necessary, adjust the Choke and Feather sliders.
1243 Chapter 72 Keying, Mattes, and Masks