The ornamental design for a double towelbar, as shown and described.
FIG. 1 is a front perspective view of a double towel bar according to the present invention.
FIG. 2 is a front view of the double towel bar of FIG. 1.
FIG. 3 is a rear view of the double towel bar of FIG. 1.
FIG. 4 is a left side view of the double towel bar of FIG. 1.
FIG. 5 is a right side view of the double towel bar of FIG. 1.
FIG. 6 is a top view of the double towel bar of FIG. 1; and,
FIG. 7 is a bottom view of the double towel bar of FIG. 1.
The broken lines show portions of the double towel bar that form no part of the claimed design.
The double towel bar is shown with a symbolic break in its length. The appearance of any portion of the article between the break lines forms no part of the claimed design.