The ornamental design for a tie-down, as shown and described.
FIG. 1 is a perspective view of a first embodiment of a tie-down design, as viewed from the right-front side.
FIG. 2 is a front view of the first embodiment of the tie-down design. The back view of the tie-down design is identical to the front view.
FIG. 3 is a top view of the first embodiment of the tie-down design.
FIG. 4 is a bottom view of the first embodiment of the tie-down design; and,
FIG. 5 is a right side view of the first embodiment of the tie-down design. The left side view of the tie-down design is identical to the right side view.
The broken lines illustrate portions of the tie-down and form no part of the claimed design. Broken lines may show structure that is not part of the claimed design; but used to show environment in which the design is used. The views or portions of the tie-down not illustrated form no part of the claimed design.