A great page on properly identifying copperheads from rat snakes.
It is startling to walk into the chicken coop and come face to face with a large rat snake though, especially since they often look very much like a dangerous copperhead. How does one decide which is which?
Rat snakes are not poisonous. They will bite when startled or threatened and the bite looks very much like a human bite on the skin. It lacks the two distinct fang marks of a poisonous snake. While it does hurt it is not going to make you sick. Just wash the area carefully with soap and water and watch for signs of infection as you would with any other wound.