Learn from mistakes I have made.....Self tapping Screws are good....who could argue, but do not tighten them too much, especially with power driver, splits the sleepers...I have several. You do not need too many screws, since gravity is on your side and the track wants to stay where it is, every 12 to 18 inches is more than enough in my experience. I put the screws in the centre of the sleepers which works fine except where you are putting rack pieces in which screws can foul, then it is two screws, one on each sleeper on the outside of the rails.