As previously mentioned, lines are made from points. Now that we are on “line point insertion” mode, click on the canvas, then click again in another place. You should now have a straight line between 2 points. You can extend your line by clicking where needed. You will see the line is made up from straight segments between line points.
To finish a line (i.e, to exit line point insertion mode) you can a) press Esc key, b) click again on the last point you made. Red box at the bottom of the window is green now, and you are back on “select object” mode. You can press Ctrl-L again to insert another line, or click on objects to select and edit them.
To delete a entire line with all its points, select the line and press Ctrl-D, or go to “File commands control” panel and click on the trash can to delete selected object.
When clicking on a line, there will always be a selected point. You can identify it because it has a red circle. Usually you click on the point of interest. If you click on the line itself, then next point towards end of the line will be selected.
When a line point is selected, you can move it by dragging. Try it now. As you see, you can select and drag any point on any line.
To delete only a line point (not entire line) select it, go to “Line control” panel, click on edit line button and select “Delete point” from the drop-down menu.
To insert a new point in the line, you must select the point next to desired place towards the end. Then go to “Line control” panel, click on “Edit line” button and select “Insert point”. Now you can click on the line to insert new “insert point” then click in desired place. When finished, you can press Esc key or click again on the point you selected at beginning.
You can split the lines. Select the point where the cut will be done. Then go to “Line control” panel, click on the “Edit line” button and select “Split line” from the drop-down menu. If you need to split the line and there is no line point at the right place, you'll need to insert a line point in this place first.
It's time to notice the yellow tick displayed at the beginning of each selected line. If you look from the first point towards next, yellow tick will be always on the left. It's important because this will be the side on which many things will be drawn. I.e., ticks for floor-step will be drawn on this side. When you are drawing cave walls, it's expected that you draw them counterclockwise, so this yellow tick should point inwards, not outwards. If you draw the line in the wrong direction, don't worry. You can go to “Line control” panel and click on “Invert” button. This effectively reverses line points order, so first point becomes last one and yellow tick will be displayed on the opposite side.
You can draw a closed area. To do it, simply click back on the first point of the line. Area will be closed and you'll be back in “Select mode” automatically. Also, you could go to “Line control” panel and check “Close”