Standard wooden entrance reducer. Depending on position it can be used as a very narrow 3/4" opening or a wider opening approximately 4" wide. Reducing the entrance of weaker hives makes it easier for guard bees to defend the hive and reduces robbing.
This entrance reducer fits best in openings that are 3/4" high as it can be inserted into the opening. When used with bottom boards with smaller openings, it must be placed in front of the entrance and may need to be secured by screws.
Note that bottom boards can vary slightly in width, so the fit may not be perfect.