Symbolism, Imagery, Allegory
When Sarah comes to the Midwest, a bit thing she misses about the Maine landscape is the sand dunes, When she tells the Witting family about how she and her brother used to slide down the dunes, Jacob hears how wistful and homesick she is and decides to make a "dune" out of hay in order to help Sarah feel more at home:
"We have no dunes here," he said.
Papa stood up.
"Yes we do," he said. He took the lantern and went out to the barn. (5.9-11)
A haystack might not be that much like a sand dune, but Sarah's game, and she slides down the haystack and has a good time. This is a way for Jacob and the children to try to make Sarah feel at home, even though she's in a strange place. They she her they understand her, and that they'll try very hard to make her happy.
When Jacob asks her how the dune is, Sarah tells him it's great:
"Fine?" called Papa.
"Fine," said Sarah. She lifted her arms over her head and slid down, down, into the soft hay. She lay, laughing, as the dogs rolled beside her.
"Was it a good dune?" called Caleb.
"Yes," said Sarah. "It is a fine dune." (5.21-24)
It may not be the same thing as a sand dune by the ocean, but Sarah appreciates the thought behind Jacob's sweet gesture. She recognizes that the Witting family is trying to make her happy, and this makes her feel closer to them.