The ornamental design for a hatholderdevice, for flat hats, as shown and described.
FIG. 1 shows a perspective view of a hat holder device for flat hats.
FIG. 2 shows a perspective view of a hat holder device for flat hats including a hat which is shown through the holder for clarity of the environmental illustration.
FIG. 3 shows a top plan view of the hat holder device for flat hats.
FIG. 4 shows a bottom plan view of the hat holder device for flat hats.
FIG. 5 shows a right side view of the hat holder device for flat hats.
FIG. 6 shows a left side view of the hat holder device for flat hats.
FIG. 7 shows a front view of the hat holder device for flat hats; and,
FIG. 8 shows a rear view of the hat holder device for flat hats.
The shade lines in the Figures show contour and not surface ornamentation.
The broken lines shown represent environmental subject matter and portions of the hat holder device for flat hats which form no part of the claimed design.