You're looking for something like this (a block drain plug):
URL for the page in case the pic doesn't stick:
http://www.f150online.com/forums/articles-how-tos/390423-howto-change-engine-coolant-antifreeze.htmlIt is not routine to pull out core plugs to flush coolant. Maybe an exception would be once the engine was removed/or a very dirty rusty cooling system where you're trying to flush the crud out of it.
I think everyone has given good advice. If you have gold looking coolant just drain and fill. You can often pull off the top radiator hose (after draining) and glance into the header tank and see the condition of the tubes. O