A word of advice -- don't believe anything the screeners tell you. (i.e. If they tell you the earth is a sphere, you should probably join the Flat Earth Society.)

Both the walk-through devices and the wands use the same technology. The wand is just "up close and personal" -- it can be used to localize metal objects.

But neither will damage mag-stripes, as neither has anything to do with magnetism. (Well, OK, maybe in a Grand Unified Theory sort of way, but not for our purposes.) If these were magnetic type devices then they wouldn't detect aluminum, right? And you can certainly make as nasty a knife with aluminum as with any other ferrous metal.

X-ray machines do pose a very slight risk to magnetic media, such as credit card mag stripes or floppy disks. However, it has nothing to do with the x-rays. Rather it has to do with the massive power supply transformers (that do generate a wallop of magnetic flux) required to generate those x-rays. But I have about 15 cards with mag strips that go through x-ray 5-10 times a week for years, with never a problem. A "theoretical" issue, I suppose. See above. The mag stripes will not set off the metal detectors. Some credit cards have metal foils which under labratory conditions might be able to be detected. But if a detector was that sensitive, then anyone with a metal filling would set off every detector in the airport. Even I don't set off the walk-through units, and I have a huge chunk of metal in my right hip (not to mention several screws and even part of a broken drill bit. The only thing that will "shield" metal is more metal, which of course would be even easier to detect. Coats, hands, wallets etc will have no effect on the walk-through units, and will only affect wands if they are so thick has to prevent the wand from being suitably close. As are all persons named Ken. It's a genetic thing. See above.