This was splendid. I had forgotten these for the moment.
"Exactly. The rails your train goes on. Well, then, 'Home Rails' would be rails at home."
"Well, I've got them at home," said Margery in surprise. "I couldn't have them anywhere else."
"Quite so. Then 'Home Rails Firm' would mean that—er—home rails were—er—firm."
"But mine aren't, because they wobble. You know they do."
"Yes, but——"
"Well, why do they say 'Home Rails Firm' when they mean 'Home Rails Wobble'?"
"Ah, that's just it. The point is that when they say 'Home Rails Firm,' they don't mean that the rails themselves are firm. In fact they don't mean at all what you think they mean. They mean something quite different."
"What do they mean?"
"I am just going to explain," I said stiffly.