To design in the rough. Whether this phrase originated in England or in America is doubtful.

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1829.  There are portions [of the Message] which bear the marks of having been “blocked out” by General Jackson.—Mass. Spy, Dec. 16.

2

1837.  The latter cantos were merely blocked out.—Lockhart, ‘Life of Scott,’ iii. 15. (N.E.D.)

3