Apple Final Cut Pro 6 - Manual (Page 668)

Chapter 18 Performing Slip, Slide, Ripple, and Roll Edits 335
III
Rolling the Position of an Edit Between Two Clips
Using the Roll tool, you move the Out point of the outgoing clip and the In point of the
incoming clip simultaneously.
In the example above, clip B gets shorter while clip C becomes longer, but the
combined duration of the two clips stays the same.
Roll edits are useful when the relative Timeline position of two clips is good, but you
want to change when the edit point occurs between them. For example, suppose your
sequence has two clips showing an Olympic diver diving into a pool from two different
angles. The first thing you need to do is adjust each clip until their edit points align on
a similar action. This is called matching on action, or a match cut. You could align the
edit point in the Timeline so that when the diver hits the water in one camera angle,
the diver is also hitting the water in the second angle. Once you have a cut point with
matching action, you can roll the edit point earlier or later to change when the edit
occurs. For example, you could roll the edit to the point where the diver is midway
between the diving board and the water.
A B C
A B C
Before edit
After edit
Roll edits are done
using the Roll tool.