The ornamental design for a sign for rack, substantially as shown and described.
FIG. 1 is a top front perspective view of the sign for rack showing my design in an environment in which the sign for rack may be used;
FIG. 2 is a top back perspective view of the design of FIG. 1;
FIG. 3 is a rear elevational view of the design of FIG. 1;
FIG. 4 is a front elevational view of the design of FIG. 1;
FIG. 5 is a right side elevational view of the design of FIG. 1;
FIG. 6 is a left side elevational view of the design of FIG. 1;
FIG. 7 is a bottom plan view of the design of FIG. 1; and,
FIG. 8 is a top plan view of the design of FIG. 1.
The portions of the FIGS. 2-8 shown in broken lines illustrate features that do not form part of the claimed design. The broken lines in FIG. 1 show both environment and portions of the article that do not form a part of the claimed design.