The ornamental design for a kickboard, as shown and described.
FIG. 1 is a perspective view from the top, front, left side of a kickboard showing an exemplary embodiment of my new design;
FIG. 2 is a front elevational view of the kickboard shown in FIG. 1;
FIG. 3 is a left side elevational view of the kickboard shown in FIG. 1, shown positioned on edge, the right side elevational view being a mirror image of the left side elevational view and not being shown;
FIG. 4 is a top plan view of the kickboard shown in FIG. 1, the bottom plan view being a mirror image of the top plan view and not being shown; and,
FIG. 5 is a rear elevational view of the kickboard shown in FIG. 1.
The broken lines in FIGS. 1 and 5 showing handles and a center aperture of the kickboard are for environmental purposes only and form no part of the claimed design for this embodiment.