U need some kind of large ( full hand size ) plastic container and a firm flat thin piece of cardboard . Trap the fly against the widow with your container , then carefully slide the piece of card under the container all the way across creating a lid on your container with the fly trapped in the container . Then press the card tight onto the top of the container with your hand , take outside and take the lid off and the fly should buzz off , also works for spiders , wasps , bees , hornets and just about any other small irritating critter 👍 .