The ornamental design for a double-sided hook, as shown and described.
FIG. 1 is a top view of my new design for a double-sided hook according to a first embodiment, a bottom view of the first embodiment being a mirror image thereof;
FIG. 2 is a first end view of the first embodiment;
FIG. 3 is a second end view of the first embodiment;
FIG. 4 is a first side view of the first embodiment;
FIG. 5 is a second side view of the first embodiment;
FIG. 6 is a top view of my new design for a double-sided hook according to a second embodiment, a bottom view of the second embodiment being a mirror image thereof;
FIG. 7 is a first end view of the second embodiment;
FIG. 8 is a second end view of the second embodiment;
FIG. 9 is a first side view of the second embodiment; and,
FIG. 10 is a second side view of the second embodiment.