Does anyone know if there is any standard or norm about a
small piece of wood (I don't know it name in english)
(375x20x20 mm) which is used to reduce the entrance to the hive.
In one side it has a small ''door'' of 150x10 mm and in the other
side another small 'door' of 50x8 mm.
        Here beekepers put it in the entrance of the hive to reduce it
in certain seasons to avoid other foreign bees come in to robe honey.
        The height (10 mm in one case, 8 mm in the other) seems to be
arbitrary. Thats the reason I am asking for the norm.
        Any help or sugestions are welcome.