Gravity Knife

FIG. 1 is a front, right and top perspective view of a gravity knife, showing my design. FIG. 2 is a rear, left and bottom perspective view thereof. FIG. 3 is a front elevation view thereof. FIG. 4 is a rear elevation view thereof. FIG. 5 is a left side elevation view thereof. FIG. 6 is a right side elevation view thereof. FIG. 7 is a top plan view thereof. FIG. 8 is a bottom plan view thereof; and, FIG. 9 is an enlarged view of detail 9 in FIG. 1 . The dashed broken lines depict portions of the gravity knife that form no part of the claimed design. The dot-dash broken lines in FIGS. 1 and 9 depict the boundaries of the enlargements that form no part of the claimed design.