You must have a scribble or line drawn to use the Split Line tool.
*NOTE: will only work on scribbles or lines.
1. After you have drawn your line, choose the Split Line tool from the Menu
2. Click along the line where you would like to have the line cut once or multiple times
3. Click on the eraser tool from the menu bar
4. Click the eraser on the portion of line you would like to erase