These wood entrance screens can be used to help protect small hives from strong hives that rob them of all the honey. If you do not stop or prevent robbing, a hive can be decimated within a few hours. The mesh entrance covering allows robbers to smell the colony and come to the front without allowing access. Your colony has an entrance at the top to find their way in and out safely.
These work best if you can place them on overnight before the bees are flying so your bees can find their way out and back in with ease. If you install them mid-day, your workers will also be on the screen trying to find their way in.