I claim the ornamental design for a sliding diagonal gauge for handicrafts, as shown and described.
FIG. 1 is a perspective view of a sliding diagonal gauge for handicrafts according to my design, the gauge including a ruler and a slider which is slidable on the ruler;
FIG. 2 is a front view of the same gauge;
FIG. 3 is a rear view of the same gauge;
FIG. 4 is a left side view of the same gauge, which is symmetrical to a right side view;
FIG. 5 is a top plan view of the same gauge;
FIG. 6 is a bottom view of the same gauge;
FIG. 7 is another front view of the same gauge with the slider moved to a distal end of the ruler; and,
FIG. 8 is a front view of a modified ruler that is replaceable for the ruler of the gauge shown in FIGS. 1-7.