The truth is that a range of sizes will work for the chicken door. The door should be at least 8 inches wide and up to 12 inches tall. My recommendation comes from experience building a coop and the book Poultry House Construction.
Pan-fry a T-bone steak quickly over high heat. Heat the pan on the stove top on high, then place the steak in the center of the pan. This sears one side of the steak almost immediately. Turn the steak after 6 to 8 minutes using tongs so you don't puncture the meat and let the juices escape. Let the steak fry for another 6 to 8 minutes.
Let the steaks grill for 3 minutes for medium-rare or 4 to 5 minutes for medium. Cook the steaks until a meat thermometer inserted reads 145 degrees Fahrenheit for medium-rare, but it's recommended to cook the meat to medium or 160 degrees Fahrenheit to avoid food poisoning.