E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.
Rail.
To sit on the rail. To shuffle off a direct answer; to hedge or to fence; to reserve the decision of one’s vote. Here rail means the fence, and “to sit on the rail” to sit on one side. A common American phrase.
1
“If he said ‘Yes,’ there was an end to any church support at once; if ‘No,’ he might as well go home at once. So he tried to sit on the rail again.”—T. Terrell: Lady Delmar, chap. i.
