The ornamental design for a cover for a rack-mount device, as shown and described.
FIG. 1 is a perspective view of a cover for a rack-mount device.
FIG. 2 is a front view of the cover for a rack-mount device of FIG. 1.
FIG. 3 is a left view of the cover for a rack-mount device of FIG. 1.
FIG. 4 is a right view of the cover for a rack-mount device of FIG. 1.
FIG. 5 is a top view of the cover for a rack-mount device of FIG. 1.
FIG. 6 is a bottom view of the cover for a rack-mount device of FIG. 1; and,
FIG. 7 is another perspective view of the cover for a rack-mount device of FIG. 1.
The broken lines in the drawings depict portions of the cover for a rack-mount device that form no part of the claimed design. The additional set of broken lines showing a rack-mount device in FIG. 7 illustrate environment and form no part of the claimed design.