The ornamental design for a reusableboxblank, as shown and described.
FIG. 1 is a top plan view of a reusable box blank showing the claimed design;
FIG. 2 is a right side view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a bottom plan view thereof;
FIG. 5 is a front view thereof, taken from the left side of FIG. 1; looking at the end of the reusable box blank which forms the top of the box;
FIG. 6 is a rear view thereof, taken as if from the right side of FIG. 1, looking at the end of the reusable box blank which forms the bottom of the box;
FIG. 7 is an enlarged detail view of the portion designated in FIG. 3, the left side view; and,
FIG. 8 is an enlarged detail view of the portion designated in FIG. 6, the rear view.