How to fix a squeaky carpet floor with This Old House

Watch this video from This Old House to learn how to fix a squeaky carpet.
Steps:

1 Use a hammer to locate a floor joist within the squeaky section of floor.
2 Tap the carpeted floor with the hammer and listen for dull thud, indicating a joist below.
3 Chuck the joist-finding screw into the drill/driver.
4 Drill a hole through carpeting and subfloor and into the joist; if you miss the joist, move over a couple of inches and try again.
5 Once you find a floor joist, measure over 16 inches and locate the next joist.
6 Press the tripod-shaped alignment and depth control fixture firmly into the carpet directly over the joist.
7 Use the drill/driver to drive a scored screw down through center of fixture until the screw bottoms out.
8 Drive screws into all the joists within the squeaky section at both ends of the room.
9 Run taut strings from screw head to screw head across the room, indicating the joists below.
10 Using the alignment and depth control fixture, drive scored screws along the strings spaced 8 inches apart.
11 Hook the screw gripper on the fixture onto each protruding screw, then rock the fixture back and forth to snap off the screw head.