Susan, how do you know they're rats and not mice? Did you actually see them, or were there other signs? Here in UK rats carry Weil's disease, so you're wise to take steps to get rid of them. I used to live in a huge area of wild land, and rats often got in. I never ever left food out at night, but put it all in sealed plastic bins. I once had a rat clinging on to the back of my tall fridge, the cats had chased it up there! I opened the back door and wheeled the fridge backwards into the opening. The rat then scarpered. Are you scared of them, or just disgusted? I'm not scared, but find them dirty creatures.