I found this post, I think maybe that's explaining the same thing that you were above Pisces:
RAOBF Cheat Sheet in subsim forum
and that although this is in SH5, the principle is about the same?
So, a RAOBF is for calculating Range and AOB.
Is the item on this thread (Absolute/Relative/AOB Dial) the same thing as an Attack Disc or are they different? Looking at the first item in Solution Solver 2.3, that looks similar to the Absolute/Relative/AOB Dial.
How's it used please?
(Sorry for the daft questions, thanks)
edit: Actually, I see Gutted has put a video up on this thread so maybe that'll help explain it a bit
http://www.subsim.com/radioroom/showthread.php?t=240575
Thanks though, I like the idea of the wooden discs.