I based this on the robber screen on Michael Bush's website. Made with 1x2 and 1x4 pine. Screen, staples, nails. Cut with hacksaw, pocketknife and file (file was to help with the notch at the top). Width of the BB was 16 1/4". The width of the inner portion of the BB was 14 1/2". I made the 1x4s 7". The length of the bar that forms the bar at the bottom on the back of the screen was 10 1/2" (IIRC).
The fit wasn't too great, mainly because when I last moved the hive, I had some nylon screen used to cover the entrance that required extensive stapling. I was removing the staples last night, but due to the quantity of bees spilling out the front in the dark, and their anger, I decided duct tape might represent the better part of valor.
The last picture was this morning. It seemed the bees were having trouble finding their way out of the hive. I will see if they have learned anything by this evening.