The plug-in was originally named vertical and normal line tool. After 2.0, it was renamed three line tools, and the icon was added.
Vertical Lines by Length（Vertical Lines by Length）Animation Tutorial
You can pick any point in the scene and draw a vertical line by the length of the input line.
Vertical Lines by Elevation（Vertical Lines by Elevation）Animation Tutorial
You can click any point in the scene, and then draw the vertical line from the point to the elevation by entering the absolute elevation.
Line on Normals（Line on Normals）Animation Tutorial
You can directly select points, lines and faces in the scene, and then enter the length to quickly draw normals.
