Q: FCP X slug?

Option w, or go to edit "Insert Gap."

Use the position tool (not the selection tool) to move a clips apart.  This creates an empty placeholder between the clips on the timeline, which is funcitonally the same as a slug in FCP 7.

Tom

Or just use the Positon Tool (p), then when you move the clips as needed, FCP X will automatically add the filler for you.

EDIT: Sorry for the duplication Tom, I was typing too slow :-)

Just a point of clarification:  The gap clip in FCP X is not the same as slug in FCP 7.  Slug is opaque, and the gap clip is transparent.

Andy