The ornamental design for a horizontalbollardadapter, as shown and described.
FIG. 1 is a front, top, left side perspective view of a horizontal bollard adapter of our design.
FIG. 2 is a front, elevation view of a horizontal bollard adapter of our design.
FIG. 3 is a rear elevation view of a horizontal bollard adapter of our design.
FIG. 4 is a left side, elevation view of a horizontal bollard adapter of our design.
FIG. 5 is a right side, elevation view of a horizontal bollard adapter of our design.
FIG. 6 is a top plan view of a horizontal bollard adapter of our design.
FIG. 7 is a bottom plan view of the horizontal bollard adapter of our design. The broken lines defining the central portion of the bottom view are for illustrative purposes only and form no part of the claimed design; and,
FIG. 8 is a rear, top left side perspective view of the a horizontal bollard adapter shown in an alternate state of use. The broken lines showing a post in FIG. 8 illustrates environment of the article and form no part of the claimed design.