US D630699 S1
The ornamental design for the bow tightener, as shown and described.
FIG. 1 is a perspective view of a bow tightener showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a left side elevational view thereof, the right side being a mirror image thereof;
FIG. 4 is a rear elevational view thereof; and,
FIG. 5 is a bottom plan view, the top plan view being a mirror image thereof.