The ornamental design for a fasteningdevice, as shown and described.
FIG. 1 is a front perspective view of a fastening device.
FIG. 2 is a top view of the fastening device shown in FIG. 1.
FIG. 3 is bottom view of the fastening device shown in FIG. 1.
FIG. 4 is a left side view of the fastening device shown in FIG. 1.
FIG. 5 is a right perspective view of the fastening device shown in FIG. 1, showing the opposing ends coupled together.
FIG. 6 is a bottom view of the fastening device shown in FIG. 1, showing the opposing ends coupled together; and,
FIG. 7 is a right side view of the fastening device according to FIG. 1, showing the opposing ends coupled together.
The broken lines in the drawings illustrate portions of the fastening device and form no part of the claimed design. The right side view of the fastening device is a mirror image of FIG. 4.