To illustrate:
Plotting your course ...
As in Nisgeis' example, you've set a course to the north using the
navigator's compass. Since the course line only extends to the center of the compass rose, your true heading must be read along the back side.
Taking a target bearing ...
True bearing to the target is about 307 degrees ... again measured on the back side.
Measuring target heading ...
This is the easiest method to plot your target's course ... anchor the line on your first fix, drag the compass over the target, then read the back side (in this case, about 089 degrees). If you like, you can also enter this target heading into the TDC by adjusting AOB.