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

The spark led them to the bench under the big tree on the Green. Then it simply waited there.

Warm wind blew the Green away, and the ground under their feet was somewhere else, the day before.

They were standing in a long, straight street. The houses on both sides were tall and plain, made of red baked bricks, all exactly the same size. Down the middle of the street ran a deep trench, and builders were lining it with more red bricks, to make a drain with a lid on top.

A boy their age was standing by the trench with a long wooden stick. In the wall behind him, one cracked brick had been taken out and a new one put in its place. Somebody had scratched a tiny hammer beside it.

"I carry messages for the builders," said the boy. "They're making a drain all along this street. One team started at this end. Another team started at the far end. Tomorrow they meet in the middle."

"What happens if they don't fit?" asked Inkling.

"Then when the rains come, the water will spill out of the gap," said the boy. "It'll flood the street, and get into people's houses."

Lan knew what the boy needed. There was one in her pencil case at school.

"I know what that means!" said Lan. "I'll go first. What you need is a..."

She said the word before she had looked.

Bzzz.

Lan went pink. Inkling squeezed her hand.

"The door," said Inkling kindly. "Only the question."

"The drain has to be the same width all the way," said the boy. "Our builder says four hands wide."

He ran all the way down the street to the other team and told them. "Four hands wide!"

The other team's builder nodded and spread her hands across the trench. One, two, three, four.

But her hands were much bigger than his team's builder's hands. When the boy ran back and looked, her half of the drain was wider. The bricks would never line up.

"Then we'll use sticks," said the boy. "Sticks don't change."

Each team cut a stick as long as its own builder's arm, from elbow to fingertips. They measured every brick and every bit of drain with their own stick.

It half worked. All the bricks in each half matched each other perfectly.

But the two sticks were not the same. One was fifty fingers long. The other was forty-six. Ten of one stick were forty fingers longer than ten of the other.

"The halves still won't meet," said the boy.

Inkling did not name anything this time. She asked questions instead.

"I noticed something," said Inkling. "Why didn't the hands work?"

"They were different hands," said the boy.

"And why didn't the sticks work?"

"They were different sticks."

"So is there one length both teams could use? Not two lengths that are meant to be the same. One." Then she stopped. "Wait, I can name it. They need one length. The same one, for everybody."

The sun went down over the flat roofs. The builders put down their tools.

"Tomorrow they'll meet crooked," said the boy. "And when the rains come, the water will pour into the street. Into the houses. Into everything."

Lan looked at the boy's stick. There was only one of it. The other team was all the way at the other end of the street.

"Can I ask you something?" said Lan. "The other team can't use your stick. There's only one. But could there be two sticks that really are the same?"

"How?" said the boy.

"If you made the second one from the first one," said Lan.

"Lay a new stick right beside yours," said Lan. "Line up the ends. Make a mark exactly where yours stops. Then cut it there."

The boy found a straight new stick. He laid it beside his own. He lined up the ends, and made a mark, and cut it. He held them side by side.

They were exactly the same length.

He ran with the copy all the way down the street to the other team. They measured their bricks again with it, and their trench, and their mould for making bricks.

In the morning the two teams met in the middle of the street. The two halves of the drain fitted together, brick against brick.

"Even," said the builder. "Perfectly even."

A few days later the first rain came. It drummed on the flat roofs and ran down into the street. It poured into the drain, under the lid, along both halves and away. Not a drop came out of the join.

Nobody would write down the boy's name.

Warm wind blew the day before away, and the grass under their feet was the Green.

On the side of the anvil, under DOOR and OPEN, after the W and the I and the D, there was a new letter. An E.

"W, I, D, E," said Inkling. "WIDE."

"Door," said Lan. "Open. Wide."

They looked at each other.

"I wonder who's coming through," said Inkling.

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 home, Lan wanted to know if the table would fit through the door. She nearly measured it with her hands. Then she fetched Mum's tape measure, and measured the door with it too. The same tape, both times.

Tell the story back to someone. Why did the hands not work? Why did two sticks not work? Why did the copied stick work?