"What does it mean?"
"Ah, well, if you don't know that," I said, rather pleased, "perhaps I had better explain that first. 'Firm' means that—that is to say, you call a thing firm if it—well, if it doesn't—that is to say, a thing is firm if it can't move."
"Like a house."
"Well, something like that. This chair for instance," and I put my hand on her chair, "is firm because you can't shake it. You see, it's quite—Hallo, what's that?"
"Oh, you bad uncle, you've knocked the castor off again," cried Margery, greatly excited at the incident.
"This is too much," I said bitterly. "Even the furniture is against me."
"Go on explaining," said Margery, rocking herself in the now wobbly chair.
I decided to leave "firm." It is not an easy word to explain at the best of times, and when everything you touch goes and breaks itself it becomes perfectly impossible.
"Well, so much for that," I said. "And now we come to 'rails.' You know what rails are?"
"Like I've got in the nursery?"