#8 self drilling screws. #8 refers to their size, they are available in different lengths. You get a Phillips screw bit for your drill and the screws will "self drill" themselves right in. You don't need to drill a hole first, the screws drill the hole themselves. They look like this:
http://www.mcfeelys.com/product/PL2-0804/8-18-x-12quot-Pan-Self-Drill-Screws
You can get them at Lowes, Home Depot, your local hardware store. They save a lot of time cause you hold it, put drill on it, zip one in, and then go to the next.
