I claim, the ornamental design for a fence rail, as shown and described.
FIG. 1 is a perspective view of the design of the fence rail;
FIG. 2 is a right side view of the fence rail, with the fence rail being broken to indicate an indefinite length, the left side view of the fence rail being a mirror image of the right side view;
FIG. 3 is a front view of the fence rail, which is a mirror image of the rear view; and,
FIG. 4 is a top plan view of the fence rail, with the fence rail being broken to indicate an indefinite length, the bottom plan view of the fence rail being a mirror image of the top plan view.
The broken lines are for illustrative purposes only and form no part of the claimed design.