The ornamental design for a tie down device, as shown and described.
FIG. 1 is a front perspective view of a tie down device.
FIG. 2 is a top plan view of the tie down device.
FIG. 3 is a front elevational view of the tie down device.
FIG. 4 is a right side elevational view of the tie down device.
FIG. 5 is a bottom plan view of the tie down device.
FIG. 6 is a left side elevational view of the tie down device.
FIG. 7 is a rear elevational view of the tie down device.
FIG. 8 is a back perspective view of the tie down device; and,
FIG. 9 is a top plan view of the tie down device utilized to secure an object.
The broken lines shown in the figures represent portions of the tie down device, connectors, and an object secured by the tie down device and connectors that form no part of the claimed design.