This moving screen is actually two pieces of equipment. Beekeepers who move their bees can leave the screen on and open and close the doors whenever they want to go. At the end of the season when robbing is prevalent you can eliminate robbing by putting the screen on your colonies and opening the top exit above the aluminum curtain.
These robbing screens work great. If your hive is getting robbed, just set the screen in front of the entrance and open the top and close the bottom entrances. It stops the robbing emmediately. Great for long term use.