The benefits of a perverted education

I'm checking over some of my collection of poi, prior to running the poi workshop at Year of the Teledu (you are all coming, aren't you?).  One of them didn't have a proper adjustment for people with different length arms - most poi are easy to adjust.

I needed a sliding knot and all my poi use what appears to be the same knot, so I looked up 'poi knot' on Google with a total lack of success.

I looked at the knot more closely.  It had an odd familiarity...

I went and looked in one of my book collection.  Sure enough, it was a taut line hitch and there was the perfect diagram on how to tie it.

Which book was it?  Well, erm, I'm also helping with the bondage workshop at Teledu...