Do not try this. Do NOT try this. This isn't like playing Super Mario Bros where you have 6 lives to waste in an attempt to jump across that pit. You have ONE shot and if you get caught, you're caught. Essentially what has been recommended is trial and error. Maybe if you're lucky you might get through the gates, but it only takes one time to fuck it up and fuck yourself over. La Fours the rent-a-security-guard isn't going to be very forgiving when you're caught trying to steal, and saying "I wasn't going to steal it, I just wanted to see if I could get through" isn't the most endearing statement to make.
1. Raising your arm over the pillars is a very bad idea. You cannot see the magnetic field and you do not know how far it's going to extend. Some of the barriers have stronger fields than others, and some extend higher than others. Sometimes the pillars aren't even the real thing: the equipment is sometimes attached to the walls and go up much higher than the pillars, with the pillars just being for show to make people think they can raise their arm. DON'T BE STUPID.
2. Again, you cannot see the magnetic field. Trying to slide the merchandise through the gap at the side is a bad idea: the field is not limited by the barriers and extends to the side, and again it can go for some distance depending on the strength of the field. I'm sure you've seen it happen at Blockbuster, when the video jockey slides your movie along the counter next to the pillar so you can pick it up when you walk out: the alarm is triggered, even though it's outside the pillar. And again, you can't be certain that the pillars aren't vanity pillars with the real deal in or on the wall. DON'T BE STUPID.
3. Do not attempt to outsmart the store. You removed the one magnetic strip? Guess what: there were two. Stores are smarter than you, and when they demagnetize the strip by sliding it over their little plate, it gets all of them. Even the one you didn't see and thus left you thinking you could have stolen it. For Christ's sake, just don't be stupid!
AmadeusTheKitten: lose the temper tantrum and stop acting like you're ten. A lot of people are very stupid, and a lot of people would try it anyway. I'm trying to make as clear as possible that it is a very bad idea to attempt to shoplift this way, as you did not make it clear that the methods listed would not work. I explained why they would not work, just as you said that they might not work.