Apple Final Cut Express HD: Getting Started - Manual (Page 52)

52 Chapter 4 Basic Editing
You can mark In and Out points while you’re playing a clip or when it’s stopped.
Sometimes it’s easier to set edit points while the clip is playing, so you can set the In or
Out point immediately when you hear or see the frame you want.
Set the In point on the
frame you want your clip
to start with.
Set the Out point on the
frame you want your clip
to end with.