I'm guessing that the rules vary by organization but I don't have any idea what they are in general. I'm watching an NCAA game and the runner between 2nd and 3rd gets caught in a rundown. She gets chased to 3rd where there is already a runner, for a second both are on the base and the lead runner gets tagged, then the trail runner breaks back toward second but is way out of the base line and gets called out. When two runners occupy the same base what are the rules?