I made this huge runner duck feeder for my ducks that are outside. I had a problem where rats and mice would steal the grains from traditional feeders so i made a 1 way door that opens to the inside and traps rats if they try to climb inside. Holds about 3-4 kg of grains. It has 2 doors which can be customized with the names of your pets. I attached the door with a thin rod from a landry clip which i heated with a torch and pushed further into the its hole. It has 2 additional openings for plexiglass or glass thats cut to size so you can see the grain level without opening the box. I trained my ducks the following way: At first no lid no doors only grain inside. Then i closed the lid. After that i inserted 1 door. Then the final door. Leave the ducks some time to learn how to use the box. I let them naturally figure it out and only after that i moved  through the steps. If youre lucky you might even catch a mighty rat!