Here is a quick little example of lines.
Drag and drop the green point anywhere on the canvas, move your mouse away from the green point and left click to draw a line between your mouse pointer and the green square.
The line is just a 8x8 sprite that I moved the center to the far right edge. To draw the line I have the line face the mousepointer, and set the scale to Height 1 (or whatever line thickness you want, and for the X I use the distance between the mouse pointer and the center of the green point.
The example is far simpler than this explanatin :)
hope that helps :)