Use silicone sealer. Numerous brands available. May need to seal window and upper 4 corners of feeder and top. I have one Sweeney feeder and 3 Texas Hunter feeders. Sometimes wind blown rain will push through a corner or the window. Also, if you do get a rust spot you can seal the rust surface with a product called "Extend" by "Loctite"- you can get both from big box stores or local hardware.