Despite the seemingly endless number of tortuous traps, mutilated body parts and unceremonious deaths, the "Saw" franchise will meet its end with the opening of the final chapter, "Saw 3D" — or so we've been told.

Nevertheless, because the films are always shrouded in secrecy, MTV News sought out director Kevin Greutert to find out a few behind-the-scenes tidbits about the latest installment, beginning with the grisly details about that table-saw trap that opens the film.

"The trap that opens the movie ... was probably the most ambitious 'Saw' trap," Greutert said, referring to the two guys and a girl harnessed on all sides of a scary table saw and a cement-cutting gasoline-powered saw ready to hack them all to bits. "The idea is that it's a love-triangle soap opera played out in 60 seconds. Essentially, the jigsaw puppet Billy appears, announces both to them and to the huge crowd that starts gathering around them that they have 60 seconds to either kill one of the two dudes by pushing the saw into the other guy or letting the center saw cut in half the woman that they've both been toyed with by for however long.

"That's all well and good on paper, but as it turns out, this device was actually really difficult to build. ... You could position the things so that the blade would conceivably miss all three of the [actors]. This is kind of a good example of what happens on almost every 'Saw' trap," he explained. "Because they're very well-designed machines, but you really have to be very careful when you're conceiving and designing these things that there aren't loopholes for getting out. We have to do a lot of duct-taping on the set just to make sure that all the issues have been addressed."

Greutert said the duct-tape solution has come in handy over the years, making what looks absolutely terrifying onscreen a lot less scary on set.

"The machinery often doesn't work at all, and it's all just done with smoke and mirrors, really. In 'Saw VI,' there was a machine; Peter Outerbridge's character William and then his janitor wake up in these two traps, they have gas masks over their faces that are monitoring their breath, and then these big, metal wedges that are clamping them over the sides," Greutert recalled. "And it looked fantastic, but really, to operate the thing, we just had prop guys with metal rods that are just kind of pushing things into them. There were no working motors of any kind on the trap. It was all just kind of jerry-rigged, and so often it's like that. If the camera pans to the right just a little bit, you'll see a bunch of stage hands just physically turning gears with their fingers."

Movie magic aside, "Saw 3D" was not without a few actually frightening moments. "There's a character who is tied down with barbed wire underneath a car that's raised up on some very frail jack stands," Greutert described about one particular trap. "The car motor is running, and it's a big '70s-era El Camino, and the rear tire is inches above this person's head. When I looked at it on the set before we brought the actress in, I just said, 'How are we ever going to get this person to lie under that while we start the car and let the engine shake it on the jack stands?' I was assured that it was safe, but I wouldn't have done it for all the tea in China, to be honest," Greutert admitted. "And this girl, she agreed that it was really terrifying, but she did it, and more power to her. She screamed her head off, and I don't think they were fake screams."

Check out everything we've got on "Saw 3D."

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