In a horror franchise, the production designer is arguably more important than a director or even the screenwriters.

The inanities pouring out of the characters’ mouths only prove that exposition is a necessary evil. But a horror franchise – let’s be clear, we are not speaking about the oeuvre that includes Hitchcock’s Psycho or Polanski’s Repulsion – lives and breathes on the familiar, almost homely, consistency of the milieu.

Saw V recently took the unlikely cottage franchise to the summit of the business. Like the anchor in a five-man relay, Saw V had pulled in more than $55 million at the North American box office by Nov. 16, lifting the brand past those of the more venerable Halloween and Friday the 13th to become the highest-grossing horror franchise of all time. According to a Lionsgate press release, the worldwide box office is more than $550 million and counting; combined with home entertainment spend, the number exceeds $1 billion. (Maple Pictures releases the film series in Canada.)

The numbers are still more impressive when you consider how little these movies cost. The budget of the original Saw was only US$1.2 million; the other four rarely strayed beyond US$10 million. How do you spend so little money? One way is to get the below-the-line guys to do the above-the-line jobs.

There have been greater directorial debuts than Saw V, but Toronto’s David Hackl comes by the position on merit. He was the production designer on Saws II through IV (all of which shot in T.O., as did the latest), and is credited as the lead sicko behind the franchise’s signature ‘traps’ that confront the hapless and eventually limbless or headless or – as viewers of Saw V saw before the opening credits – gutless characters.

‘Saw fans are always sending me ideas for traps,’ the 45-year-old Hackl told me in a recent interview. His usual reply: ‘Nice idea but it’s not a Saw trap.’

‘We like it to be very visceral,’ he says. ‘That’s what’s important for the production designer and the director: as soon as the audience sees the trap, they know what kind of trouble is coming. They know the trap is going to go off eventually. You get that feeling of being on the edge of your seat just waiting for the evil to occur.’

It’s like having a cavity filled and realizing that if the dentist were to drill just one more millimeter, you would be Dustin Hoffman in Marathon Man.

Case in point: one of the promotional stills features actor Scott Patterson with his head in what looks like a cube aquarium. In the film, two hoses lead into the chamber from two giant water bottles like the ones in your office cooler. There’s no swallowing your way out of this jam. So when the water flows, Patterson’s Agent Strahm does what anyone would do in the situation: he keeps his mouth shut and gives himself a tracheotomy with a pen.

So how does Hackl account for the success of the Saw films?

‘The original Saw set up a great premise,’ he says. As well, there is an excellent villain in Jigsaw, the deeply misguided doctor who devised the traps, along with his acolytes and copycats. Hackl credits actor Tobin Bell for creating a winning amalgam of Freddy Krueger and Hannibal Lecter. Another factor, he says, is keeping the sequels within the original’s parameters.

‘We’ve been careful to keep within the concept – not to reinvent the world,’ he explains. ‘We have not taken it out into the exterior environment or added big chases.’

Or, more important, added expense – a point Hackl readily concedes. ‘If we all of a sudden make a $25-million film, it would be far harder to make it profitable.

‘That’s a problem with many franchises. ‘Let’s make this bigger, brighter, the explosions louder.’ And you turn it into a different animal. We kept in the Saw world.’

And, like all the previous Saw films, it was all shot in one studio.

He may have finally directed a feature, but Hackl has not given up his day job. He was the production designer on the upcoming film from the director of Saw IV, Darren Lynn Bousman, whose Repo! The Genetic Opera opens in Canada Nov. 21.

As for the inevitable Saw VI, don’t look for Hackl’s name on the credits. Saw I-V editor Kevin Greutert will be directing.