Nik Wallenda's team designed a number of measures to keep him safe on his unprecedented walk across Niagara Falls. (Ida Mae Astute/ABC)

The safety device that Nik Wallenda will wear on his walk across Niagara Falls tonight will keep him from plunging 200 feet down to the rushing water below, but "it doesn't help my balance in any way," Wallenda, 33, told ABC News in an interview.

The device consists of a harness - that Wallenda will wear - connected to a lanyard that is attached to the wire. The lanyard will move behind Wallenda as he walks.

"The way the harness works is it is attached to my waist and then there's a cable that goes down to the wire and a trolley of sorts that follows me. That trolley weighs about 10.2 pounds. It actually just drags along … It still grips no matter what throughout the whole process," Wallenda explained to reporters yesterday.

Wallenda's father, Terry Troffer, is the safety coordinator for his son. He said he is confident in the equipment - but he's also confident his son won't fall.

The device will "support his weight if he were to fall off the high wire, which is pretty much impossible for Nik to do," he said.

If Wallenda did fall, the lanyard is specially designed to slow the speed of such a descent and minimize the potential for any injury.

Wallenda has never worn a tether in his high-wire performances. "There's a lot of unknowns with that tether, other than I know it'll keep me from falling in the water," he said.

At a press conference yesterday, Wallenda said he has trained with the tether.

"It's unique for sure. It's something I've had very little training on, but I feel very confident. I have trained enough that I know that it will work and I'll be successful in wearing to the other side."

Other safety measures designed by Nik's team include weighted pendulums hung at 150-foot intervals on the high wire. The 50-pound weights are engineered to prevent the wire from rolling under Wallenda's feet. The pendulums help compensate for the fact that, unlike other high-wire stunts, there won't be any stabilizers - cables connected to the ground - to steady the high wire.

"No one's ever rigged a wire this long without stabilizers," Wallenda said. "I won't have a choice but to focus."