Front surface of a window sill

FIG. 1 is a perspective view of a first embodiment of a front surface of a window sill incorporating the ornamental design in association with a window embedded in a wall (both shown in phantom);

FIG. 2 is a perspective view of the first embodiment (the wall and the window are omitted for clarity);

FIG. 3 is a front view of the first embodiment (the wall the and window are omitted for clarity);

FIG. 4 is a right side view of the first embodiment (the wall and the window are omitted for clarity);

FIG. 5 is a left side view of the first embodiment (the wall and the window are omitted for clarity);

FIG. 6 is a top view of the first embodiment (the wall and the window are omitted for clarity);

FIG. 7 is a bottom view of the first embodiment (the wall and the window are omitted for clarity);

FIG. 8 is a perspective view of a second embodiment of a front surface of a window sill incorporating the ornamental design;

FIG. 9 is a front view of the second embodiment;

FIG. 10 is a right side view of the second embodiment;

FIG. 11 is a left side view of the second embodiment;

FIG. 12 is a top view of the second embodiment;

FIG. 13 is a bottom view of the second embodiment;

FIG. 14 is a perspective view of a third embodiment of a front surface of a window sill incorporating the ornamental design;

FIG. 15 is a front view of the third embodiment;

FIG. 16 is a right side view of the third embodiment;

FIG. 17 is a left side view of the third embodiment;

FIG. 18 is a top view of the third embodiment; and,

FIG. 19 is a bottom view of the third embodiment.

The broken line showing of the wall and window in FIG. 1 represents the environment. The broken line showing of the back portion of the block is included for the purpose of illustrating a portion of the front surface of a window sill that forms no part of the claimed design. None of the broken lines form a part of the claimed design.