Thanks for the info on the knots page. I did a really good class with a guy from San Diego Fire on high angle rope rescue. I learned alot, but the need for more info (especially making sure your knots are right)! never ends!
I've just brought a copy and whilst I'm still learning to use it, it's fantastic!
In fact it's almost scary as it calculates the forces in your systems and highlights issues.
As an example here's 2 pix of a 4:1 system- one is not labelled, the other obviously is. As you can see, Rescue Rigger calculates the forces which will help you design and develop better and safer systems in the field...