The ornamental design for a rectalplug, as shown and described.
FIG. 1 is a front, top, and right side perspective view of a rectal plug showing our new design;
FIG. 2 is a rear, top, and right side perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a left side view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
The broken lines in the drawings showing portions of the rectal plug are included for the purpose of illustrating environmental structure and form no part of the claimed design.