I had never heard of these before reading a forum question about them. Basically, every hole card combo is assigned a number and if it folds around to you in the SB you can make a shove decision based on the number. If your stack is at the number or lower then you can shove and have it be EV+ even against perfect play. Then there are adjustments you can make such as dividing that number by 3 for the cutoff position.
It sounds like it was published in Sklansky's No Limit Hold'em Theory and Practice (2006). I'm just surprised that I hadn't heard of this before.