The ornamental design for a dustboot, as shown and described.
FIG. 1 is an isometric view of a dust boot, showing my new design;
FIG. 2 is a front side view of the dust boot in FIG. 1;
FIG. 3 is a back side view of the dust boot in FIG. 1;
FIG. 4 is a left side view of the dust boot in FIG. 1;
FIG. 5 is a right side view of the dust boot in FIG. 1;
FIG. 6 is a top plan view of the dust boot in FIG. 1;
FIG. 7 is a bottom plan view of the dust boot in FIG. 1; and,
FIG. 8 is an isometric view of the dust boot in FIG. 1, in a state of use.
The broken lines illustrate portions of the dust boot that form no part of the claimed design. Broken lines showing a base and top in FIG. 8, illustrate environmental structure that form no part of the claimed design.