Which trim tool produces a gap but does not change the length of the timeline?

The trim tool that produces a gap without changing the overall length of the timeline is the option that allows you to leave a gap between clips while maintaining the same total duration. This tool does not remove any media from the sequence; instead, it simply shortens one clip while leaving a space where the other clip was.

Using the overwriting method typically involves replacing existing media in the timeline with new media, which alters the sequence and its duration rather than just leaving a gap. This means that while using overwriting, you are effectively shortening the original clip and adding new content in its place, instead of creating an empty space.

In contrast, options such as ripple and extend also affect the overall timeline by adjusting the placement of clips relative to one another. Ripple trims, for instance, shift all subsequent clips in addition to changing the length of the clip being adjusted, while extend involves lengthening a clip at the expense of time from the adjacent clip.

Therefore, the tool that specifically allows for creating gaps without affecting the total length of the timeline is the one that produces an effect without altering the overall sequence duration.