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Editing Clips in the Timeline with In and Out Points
You can edit clips in the Timeline to create a precise segment into which you can insert another clip - a process called three-point editing.
To do so, click on the clip in the Timeline so it also displays in the Canvas, then start scrubbing through the clip.
Press the I Key (for IN) at the desired point where you want an inserted clip to begin. Then press the O Key (for OUT) at the point you want the inserted clip to end. You will see arrows appear in the window at the points you pressed the I and O keys.
These points can be moved by clicking and dragging on the arrows, either in the Canvas or in the Timeline.
When you then drag a new clip from the Viewer into the Timeline and do an Overwrite Edit on the existing clip that has the set in and out points, the beginning of the new clip will be inserted at the in point of the existing clip, and the new clip will be cropped so it ends at the out point of the existing clip in the Timeline.