Emily Dickinson Lexicon

RAIL, n.¹ [G. riegel, rail; bolt or bar; W. rhail.]

1. A cross beam faxed at the ends in two upright posts. – Moxon. [In New England, this is never called a beam; pieces of timber of the proper size for rails are called scantling.]
2. In the United States, a piece of timber cleft, hewed or sawed, rough or smooth, inserted in upright posts for fencing. The common rails among farmers, are rough, being used as they are split from the chestnut or other trees. The rails used in fences of boards or pickets round gentlemen's houses and gardens, are usually sawed scantling and often dressed with the plane.
3. A bar of wood or iron used for inclosing any place; the piece into which balusters are inserted.
4. A series of posts connected with cross beams, by which a place is inclosed. – Johnson. In New England we never call this series a rail, but by the general term railing. In a picket fence, the pales or pickets rise above the rails; in a balustrade, or fence resembling it, the balusters usually terminate in the rails.
5. In a ship, a narrow plank nailed for ornament or security on a ship's upper works; also, a curved piece of timber extending from the bows of a ship to the continuation of its stern, to support the knee of the head, &c. – Mar. Dict.