The ornamental design for the attachment hook ornament, as shown and described.
FIG. 1 is a front perspective view of a new design for an attachment hook ornament. An attachment hook and an attachment strap are shown as environmental material in dashed lines.
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 view thereof; and,
FIG. 7 is a bottom view thereof.
The solid line showing illustrates the claimed features within the design for the claimed article of manufacture. The dashed lines are environmental material that form no part of the claimed design.