Drawings are divided into “scraps”. Anything between a scrap/endscrap pair of lines is part of the same scrap. Into the scraps, we will find points, lines and areas. You'll see scraps and their contents in “File commands” control panel.
For simple, small caves like this, all the drawing can be done in only one scrap. However, if cave would be bigger, making only one scrap could lead to memory problems when compiling. This is not the case with our example. Also, if there were parts of the cave overlapping underlying passages, the only way to do is to have more than one scrap, because scraps can't intersect themselves (more on this later). For now, we want only to learn how to draw, so we will do only one scrap.
Go to “File commands” control panel, and press the “Insert scrap” button. The “Scrap control” panel will open. Xtherion will suggest “scrap1” as scrap's name. It's fine for now. Next, you'll need to choose a projection for the scrap. Since we are drawing cave's plan, choose “plan” from the menu (click on triangle to see it). You can press “Update” button to be sure that Xtherion will save this changes, but usually there is no need, because it's done automatically. Scrap is now created, and you can see a pair of lines in “File commands” list.