The ornamental design for a rail, as shown and described.
FIG. 1 is an end elevation view of a rail.
FIG. 2 is a bottom view of the rail of FIG. 1.
FIG. 3 is an isometric view of the rail of FIG. 1; and,
FIG. 4 is another isometric view of the rail of FIG. 1.
Portions of FIGS. 1 through 4 are shown in broken and dash-dot-dash boundary lines illustrating portions of the article and environmental subject matter that form no part of the claimed design. The appearance of any portion of the rail between the break lines forms no part of the claimed design.