I think it's time we all sat down and had a little discussion about cold air returns and their applications with regards to home heating. I have no particular reason to bring this up right now, none whatsoever. I surely couldn't have done something stupid for lack of this knowledge. No sir! That being said, do take the time to educate yourself on this important element of certain home heating systems provided you one day rent or own such a place that has one and find it prudent to know and understand its very necessary function. Here's a Yahoo! Answers
about it. Here's a fabulous picture of cold air return covers.
Here's a diagram of a home heating system.
There! Aren't we all better off now? I KNOW I AM!