The ornamental design for a heightgauge, as shown and described.
FIG. 1 is a front, right-side, top perspective view of the height gauge;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a left-side elevational view thereof;
FIG. 5 is a right-side elevational view thereof;
FIG. 6 is a rear elevational view thereof;
FIG. 7 is a bottom plan view thereof;
FIG. 8 is a rear, right-side, top perspective view; and,
FIG. 9 is an enlarged view of the area 9 in FIG. 8.
The broken lines immediately adjacent the shaded surfaces represent boundaries of the claimed subject matter, and the remaining broken lines depict environmental subject matter. The broken lines form no part of the claimed design.