The Null Segment tool allows you to draw a temporary segment on the screen. The segment is immediately removed as soon as you lift your finger. This is only for presentation purposes. It allows you to interact with the page without changing it, similar to the Null tool. One thing to note is that the Null Segment honors Snapping. If you don’t want this, simply turn Snapping off using the Header Option Button for snapping. Just remember to turn it back on later if you need it for path construction.