Final Cut Pro X: snapping
When the snapping feature is turned on in Final Cut Pro, items you move in the timeline (including the playhead, the skimmer, and selected clips) appear to jump, or “snap,” directly to certain points in the timeline. This can help you quickly line up edits with other items in the project. Snapping affects the functions of many of the editing tools in Final Cut Pro, including the Select tool, the Trim tool, the Position tool, the Range Selection tool, and the Blade tool. You can disable snapping when frame-by-frame precision editing is required.