Apple Final Cut Express HD - Manual (Page 469)

Chapter 32 Performing Slip, Slide, Ripple, and Roll Edits 469
VII
3 Hold down the Command key, then click the In point of an adjacent audio clip.
Holding down the Command key while selecting an edit point allows you to add edit
points to the current selection without deselecting previously selected edit points.
4 Use the Ripple tool to trim the above selection.
The video and audio edit points move in opposite directions, creating a split edit.
Audio-video synchronization is maintained in both clips.
Current Out point of
outgoing video clip
In point of incoming
audio clips
Intended video
edit point
Before
This clip remains
the same length.
Incoming audio clip
is trimmed shorter
from its In point.
Outgoing video clip
is trimmed shorter
from its Out point.
This clip remains
the same length.
After