The jig for cutting 4 legs at once is actually very simple, and is set into the spoil board. It is nice to use, because you can surface your spoil board as usual without affecting the jig (until the spoil board becomes too thin, and then you just replace the spoil board and cut a new pocket and glue a new jig in place.
The T-bolts simply set into the slot and turn 90 degrees to lock them in place, and the 3/8" holes are used to index the leg blanks with dowels.
This is the latest stool I made a couple weeks ago. I'm using the new jig rather than my complex aluminum jig now, because there is absolutely no set-up. I can still use my spoil board for sheet goods, but I just insert the t-bolts and cut my legs. Sorry for the poor quality picture, I tried taking a picture in the near dark with my iPhone flash.