It is called 2 heddle intermesh and i got my info from laverne waddington's 2 nd book! Find her here http://backstrapweaving.wordpress.com.
This technique allows me to put a motif on a weaving with a solid background no stripes, or dots in the background.
Started off kind of wonky, but by the time I got to the second motif I was on a roll!!!
And it is somewhat reversible also. It just depends on the design/motif.