Quote Originally Posted by vim View Post
I saw this on This Old House or some similar show.

If you know the direction of the joists, that will help.
You can use a stud finder or measure out from the wall and experiment till you find one, then use a tape to find the rest.
If you do that at both ends of the room, you can run strings between them along the joist lines.

There's a specialized screw that you can drive in and then snap off below the carpet.

Hope that helps a little.

ETA: right here
Thanks very much for the link! I found one at Ace Hardware, rushed out and got it.