(upbeat music) - Here at the United Center, the Bulls have just beaten the Knicks, but as one team heads for the locker room, another team takes the floor, literally.

Ah!

Yes!

Okay, I better get out of the way here because this crew of 50 doesn't fool around.

Tonight, we're gonna see it go from a basketball court to a hockey rink.

- Yep.

- How long will that take you?

- With the way that we work, two and a half hours max.

- [Geoffrey] Conversions Chief Dennard Jefferson knows the cold hard facts.

Where's the ice right now?

- The ice, you're standing on it.

You're right on top of it.

- What?

- Yep.

Apparently, I'm not the only one amazed by that, according to Director of Building Operations, Scott Boyke.

are people often surprised that there is ice underneath the basketball court?

- Always.

Always.

It's a common question, "Is the ice under there?"

It's under there all year long.

(upbeat music) - They only started this 15 minutes ago, and look at how much is gone already.

- Grab a corner.

We're just pick straight up.

- Oh, that's not... - Not too bad.

(upbeat music) - I just picked up the floor at the United Center.

(upbeat music) Like what was here last night?

- [Scott] We had a comedy show last night.

- And then tonight?

- We have a Bulls game.

- And tomorrow.

- We have a Hawks game.

- That's exhausting.

- It can be.

- But the grind of constant conversions doesn't seem to get to Dennard.

- Oh yeah.

I'm always hands on.

Sometimes, I gotta remind myself that I'm a supervisor.

I'm just hands on.

I love the work.

- So you love it doesn't get routine after a while, like boring?

- No.

When you love what you do, it never gets boring.

- In addition to the floor, the conversions team removes several sections of seats and a subfloor known as ice decking.

They stow everything in the storage tunnel beneath the stands.

Okay, it's starting to be more of a hockey rink now, so I gotta dress properly.

Boards and glass replace the seats and workers uncover the ice.

70 minutes in, it's looking a lot like a hockey rink.

There are rough edges to smooth out.

That's the job of Chicago's Zamboni living legend, Danny Ahearn.

- And you're a former hockey player?

- Yes.

- What'd you play?

Wait, do that again.

A knee injury ended Danny's hockey career, so he found another way to stay on the ice.

- I worked at a ice rink and that's how it started, but I learned how to do the repairs on the refrigeration system.

Actually, I was still in high school.

- Danny's biggest pet peeve is spilled drinks that trickle through the ice decking - And a lot of it's alcohol.

And what does alcohol not do?

It don't freeze.

- With the changeover complete, most of the crew has clocked out, but Danny still has some important business to attend to.

I'm riding the Zamboni!

(upbeat music) Who invented this thing?

- [Danny] Guy named Frank Zamboni.

- Did you ever meet him?

- Oh yeah.

- Really?

- Oh yeah.

- [Geoffrey] What was he like?

- Normal guy.

Smart.

- I'll say.

So how many years have you been doing this?

- [Danny] Between the stadium and here, 43.

- 43 years?

- Yeah.

(upbeat music) - And stop, two hours and 12 minutes, and I'm about to go skating.

(gentle music) I can't believe I'm doing this.

Before long, this pristine sheet of ice will be hidden again as the crew returns to transform the United Center for the next big event.

(gentle music)