Use in points and out points to determine where and how edits are inserted on the record clip. In and out points also determine what part of a source clip is used when inserting or overwriting material.
Assume you have a 200-frame source clip, but are only interested in frames 50-125. By marking an in point at frame 50 and an out point at frame 125, only frames 50-125 will be visible in your edit. The remaining frames will still be available as head and tail frames, which can be used for trimming or creating transitions.
The timeline positioner acts as an implicit in point when performing overwrite and insert edits. If there is no in or out point in the record clip, the positioner in the record clip is used as an implicit in point. The new material from the source clip is inserted at the frame where the positioner is located.
If there is no in point or out point in the source clip, the positioner in the source clip is used as an implicit in point. If there is an in point and/or an out point in the source clip, the positioner is ignored.