I don't have a rat problem so I don't have any kind of cap on the top of mine. Just my large mouth funnel hanging on a hook directly above the top so it's easy to fill. A cap on top or hardwire would prevent them from crawling inside the PVC pipe but you would have to remove it every time you wanted to fill the feeder up and they could still eat food out of the sewer cap at the bottom where the chickens have access. I'm not sure there's any kind of feeder that would keep rats out entirely.It there a way to stop rats getting at the food in the containers ? I liked your pvc post CSisley. would a hard wire prevent them getting into the tube ? a Screw cap on top is easy enough ?