I need to run ROMEX (type NM) cable through holes drilled in the floor joists in my unfinished basement. I've read all about drilling through the center of the joists, not near the top or bottom. My question is about drilling holes through *double joists". In my older home, this was never done: with great difficulty, cables were routed over the top of the double joists. In this circa 1983 home, sometimes cables go over the double joist, and sometimes through. What are the rules here?