Okay, this is the same thing I say to every member, read this article! It decimated my rat problem! I suggest the feeder (Grandpas feeder) that is suggested in the article! I bought one and love it! Fo more reasons then just keeping out rats! Look
here for the Q&A section, and
here for the purchase section! There is also another brand of feeder that will probably come up here, one made my Al Gerhart with also looks well made. You want to do everything that the article says, I highly suggest not using poison, for all the reasons and more listed in the article. I hope this helps! Article-
https://backyardchickenproject.com/how-to-get-rid-of-rats-in-the-chicken-coop-the-definitive-guide/