Using Selection Sliders
The Selection Sliders, a start selection slider and an end selection slider, are not always visible. They have a red handle. To activate and use them, click the Show/Hide Selection Sliders button from the Timeline controls at the top left corner of the Timeline (last button) or select Selection Sliders from the View menu. The shortcut key F5 can also be used. The selection slider selects a range in the Timeline. You can drag and move the handles of the start and end sliders to cover a desired portion of the Timeline. The range of a track that is selected appears with a dotted rectangle spanning the selection sliders. The selected range can be edited. The Lock and Hide options modify the way a range is selected. Learn about the Lock and Disable Options…
Selection sliders can be used when you want to cut, copy, paste and delete an entire range of the Timeline.
When Selection Sliders are active and you make a movie, only the range of the Timeline that is covered by the Selection Sliders is considered. This option is very handy when you want to make a movie of only a particular portion of the Timeline.