The ornamental design for a dual sided footfile, as shown and described.
FIG. 1 is a perspective view showing my new dual sided foot file design;
FIG. 2 is a top view showing my new dual sided foot file design;
FIG. 3 is a side view showing my new dual sided foot file design;
FIG. 4 is a bottom view showing my new dual sided foot file design;
FIG. 5 is a front end view showing my new dual sided foot file design; and,
FIG. 6 is a rear end view showing my new dual sided foot file design.
The broken lines immediately adjacent the shaded areas represent the bounds of the claim and all other broken lines are for illustrative purposes only. None of the broken lines form a part of the claimed design.