The ornamental design for a shinshackle, as shown and described herein.
FIG. 1 is a top and side perspective view of a shin shackle showing a new design;
FIG. 2 is a top and back perspective view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a front elevational view thereof;
FIG. 6 is a rear elevational view thereof; and,
FIG. 7 is a left side elevational view thereof with the right side being a mirror image.
The portions of the broken lines depicting a human leg in FIGS. 1 and 2 depict unclaimed environmental subject matter. The broken lines on a shin shackle in FIGS. 1-4 represent claimed stitching.