The outside studs go into the water jackets, but the studs don't bottom out in the water jacket. It's pretty simple; once the drill bit comes out the other side of the stud, stop drilling. I have done this method in the past, so I can assure you that it works. Otherwise, if the extractor breaks, you won't be able to remove it. I'm not trying to be a smart a$$, just describing my experience with them.
