The hammer rang once. A spark jumped off the anvil and did not go out. It waited. They followed.

It skipped across the Green and into the print shop. It stopped on the long table, next to a square of paper.

"Fold me, I won't mind," said Kami.

"Somewhere with a big machine," said Lan. "A noisy one."

"Then fold me in half," said Kami, "and fold two corners down into a roof."

They folded Kami in half, top to bottom. They folded the two top corners down until they met in the middle. A little pointed roof.

The last crease went flat, and the paper opened like a door.

The first thing was the smell. Ink, oil and sawdust, all at once.

They stood in a dusty room with one grey window. A huge black iron press stood in the middle. A man in shirt sleeves pulled its long handle, and it went clunk, then creak.

"England," said Kami. "London. The year is 1871."

Small blocks of wood lay on a bench. Each one had a picture cut into it, back to front. On the wall hung a print of a walrus walking beside a man in a folded paper hat.

A girl in a white apron held a long sheet of newspaper. She had a smudge of ink on her cheek.

"I'm Nell," she said. "That's my dad. He prints the pictures so the engravers can check them. Look at his hair."

They looked. It was full of black spots.

"The ink flies off the rollers," said Nell. "He always wears a paper cap, but he left it at home. And tomorrow is the big day. The pictures for a new book get printed."

"So make him a new cap," said Lan.

Nell held up the newspaper. "This is the only paper I'm allowed to use. The rest is for printing. And it's long, not square."

"I'll do it!" said Lan. "I promise. I'll make it square, like Kami." She grabbed the big scissors from the bench.

"Look where the line stops," said Mark. He pointed at the print on the wall. "That hat has no cut in it anywhere. Read the drawing first."

Lan stopped, with the scissors open. If she cut the sheet, there would be a square and a long thin strip left over. A strip was no use for anything.

"I promised before I checked," she said, and put the scissors down. "Sorry, Nell."

Mark stood in front of the print of the walrus and the man in the hat.

"Read the drawing before your hands move," said Mark. "The roof of the hat is a point made of two corners. And the bottom is a brim, folded up all the way round."

"Two corners," said Inkling. "Wait, I can name it. It's a roof."

"And a roof like that needs a sheet longer than it is wide," said Mark. "Folded in half, with the fold at the top. Every line on the drawing has a job."

Nell looked at her long newspaper. "So it's the right shape after all."

Cornelia sat on the bench beside the newspaper.

"Corners first, always," said Cornelia. "But first, edges. Bring the top edge down to the bottom edge. Make them meet exactly."

Nell folded the sheet in half. Now the fold was at the top.

"Now one top corner, down to the middle line," said Cornelia.

Nell folded the left corner down until its edge lay on an imaginary line in the middle. Then she folded the right corner down to meet it.

"Three folds," said Inkling.

But the second corner had gone too far. It slid right past the middle line, and the roof leaned over like a chimney about to fall.

"It looks drunk," said Lan.

Nell's cheeks went pink. "Dad needs it tomorrow."

"Crooked is just a first go," said Crinkle. "Open it up gently. Smooth it out and try again. The crease remembers."

Nell lifted the corner back up and folded it again, slowly, until it just touched the first corner on the middle line. The roof stood up straight and sharp.

At the bottom of the hat, two strips of newspaper still stuck out.

"Hold it still," said Presso. "Now press it flat."

Nell folded the front strip up over the corners and pressed it. Then she turned the hat round and folded the back strip up behind, and pressed that too.

"One fold in half," counted Inkling. "Two corners. Two brims. Five folds."

Nell opened the bottom. It was a hat, pointed on top, with a brim all round.

"Every fold makes me something new," said Kami. "But a hat has one real test. It has to stay on while you work."

Nell carried the hat to her father. He laughed and put it on.

All afternoon he worked the press. He bent over the rollers. He pulled the long handle. He leaned down to look at every print. The hat never fell off.

At the end of the day he took it off. Inkling looked at his hair first, before she said anything. The brim was speckled with black. His hair was clean. "Now it's a hat," she said.

"I'm still one piece of paper," said Kami. "Even when I'm not a square."

Nell's father hung the hat on a nail for the big day.

Lan found a plain square in her pocket. They unfolded it flat, and the door closed behind them.

The spark dimmed to a warm dot and settled back on the anvil. The Green was just the Green again.

Back on the Green

At the print shop, Lan found a long sheet of old paper. She folded a hat from it, without cutting a thing, and wore it while she inked the rollers.

Tell the story back to someone. Why was the long sheet the right shape after all?