by Stephanie CrosbyThe final piece of structural steel will be lifted into place on the downtown Louisville arena today. A ‘topping off’ ceremony is set for this afternoon. It’s closed to the public.Arena General Manager Ted Nicholson says it will include arena, city and university leaders.“We’re going to celebrate it by having the final structural piece of steel lifted up in front of dignitaries and the arena workers, after they have actually signed the beam," says Nicholson, "and it will have a flag with it and a small tree.”The tree symbolizes respect for the earth, and will be planted in Waterfront Park after the ceremony.The arena is set to be fully enclosed by April and opened in November.