Qb takes snap and attacks EMLOS. His aiming point is 2 yds. outside the original alignment of the play side end. IF DE comes upfield to QB, the QB will throw the shuffle pass to the back. The RB's land mark is inside hip of PST. BSG pulls and leads for the RB. If the DE crashes inside following the down block of the PST, the QB keeps and gets his butt upfield! The play side slot receiver takes bucket step and gets in pitch relationship with QB. He looks for pitch!!! This is out of spread gun.
Out of an EMPTY GUN the play works identically. The 3 receiver on the trips side replaces the RB as the guy who gets the shuffle from the QB. On the snap, he runs down the LOS with his land mark the inside hip of the playside tackle. This example features the play being run to the open side, away from the TE who is flexed to about 6 yds.
Here is a video link from the thread from another poster, which is very helpful. Also, below I have shown a couple of (very quick, sorry for the sloppiness) drawings to help show what this looks like.