The ornamental design for a shelf, as shown and described.
FIG. 1 is the front perspective view of a shelf showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left-side view thereof;
FIG. 5 is a right-side view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 illustrates that the shelf is in use in a door of a refrigerator.
The surface treatment of the shelf shown in the figures forms no part of the claimed design, a shelf according to the claimed design may have any surface treatment.
The inventors contemplate that other embodiments of their design may include any part, portion, element or combination of elements of the claimed design.
The broken lines are for the purpose of illustrating the environment of the article only and form no part of the claimed design.