Robbing is always a big problem in my bee yard once it turns hot and dry, and I have resolved to make robber screens for every hive before it gets started.
I use all 8 frame mediums so the really tall ones aren't the best option for me.
The simplest version is just 4 pieces of wood and a screen - does not restrict the entrance...
From - beekeepingforums - Robber-screen-moving-screen
The version on Michael Bush's site forms a labyrinth to get the entrance smell farther from the opening of the screen...
From - Miscellaneous Bee Equipment
While simple is good when you are making a bunch of something it's even better when they all work as needed. Anyone have experience as to what works best? Anyone have a better design?