The ornamental design for a shaft, as shown and described.
FIG. 1 is a top, right, frontal perspective view of a shaft showing my new design with portions being shown in cross-hatch to represent orange colored surfaces;
FIG. 2 shows portions of the shaft of FIG. 1 enlarged with center section excluded for clarity of illustration where portions thereof are shown in cross-hatch to represent orange colored surfaces;
FIG. 3 is a top view of the shaft of FIG. 2 shown enlarged with center section excluded for clarity of illustration where portions thereof are shown in cross-hatch to represent orange colored surfaces the bottom view being identical;
FIG. 4 is a frontal view of the shaft of FIG. 2 shown enlarged with center section excluded for clarity of illustration where portions thereof are shown in cross-hatch to represent orange colored surfaces, the rear view being identical; and,
FIG. 5 is a right end view of the shaft of FIG. 2, the left end being identical, where portions thereof are shown in cross-hatch to represent orange colored surfaces.
The broken lines showing portions of the shaft are included for the purpose of illustrating portions of the article and form no part of the claimed design.