Quick -- what does the V in V-chip stand for? Does your TV have one? Do you know how to use it? If you flunked this test, you're like most moms and dads. But if you want to regulate what your kids view, it's your first line of defense -- and it's free. Since 2000, all sets 13 inches and larger come with the device, which lets you block programs according to rating. (All broadcast and cable shows have one of six labels, from toddler-friendly TV-Y to graphic, explicit TV-MA. See www.fcc.gov/vchip.) You can restrict certain channels or selectively screen out profanity, sex, or violence (yes, that's what the "V" stands for). Just use the remote to bring up an on-screen menu, choose your settings, and lock them in with a pass code, which even the most tech-savvy teen won't be able to circumvent.