karma: I think there is a terminology gap here. Here are some possibilities:
1. Moving Screen. These are generally attachments to the primary opening that can be shut off easily to trap ALL bees inside. Many commercially available ones can also serve as "robbing screens" because they create confusion to non-resident bees trying to access the hive. A metal or plastic flap can be moved to close off all entrances, thus converting the "robbing screen" into a "moving screen."
2. "Entrance Guard with Excluder." Mann Lake sells this product. It is a device placed across the entire entrance of the hive that will allow worker bees to enter and exit the hive, but has a portion of a queen excluder that prevents a queen from leaving the hive. I actually have one of these. I only use if when I catch a swarm. I hive a new swarm and place the Entrance Guard with Excluder across the opening for about a week. This helps force the swarm to accept the hive I have provided them.
3. Entrance Reducer. This is a strip of wood or plastic that has 2 openings cut into it and can be positioned at the entrance of the hive in 2 different positions. They are used to control the size of the entrance to the hive and are changed seasonally to help colonies prevent robbing. All bees, including the queen, can pass through either opening setting of an Entrance Reducer.
4. Mouse Guards. This is a strip of metal (usually) that fits across the entire opening of the hive that has holes in it large enough for all bees to pass through, but too small for a mouse to pass through. There is often a metal slide that will cover the holes so that it can also serve as a moving screen.
I hope this answers your question or makes it easier to clarify what you are asking.
