I'll just add that in order to shoot this stop shot effectively, you must hit whitey about 3/4 of a tip or so below center ball (due to the length of the shot and the amount of cloth friction that whitey will encounter along its route to the object ball tending to undo the backspin) and remember to stoke firmly through whitey... in other words... don't forget to finish your stroke... and whitey will stop effectively... just on your side of the object ball.