Cheese Sauce II

2 tbs butter or margarine

2 tbs flour

1/2 tsp Salt

1 cup milk

1/2 cup shredded Swiss cheese

Melt butter in 1-quart saucepan. Stir in flour and salt to form a paste. Gradually add milk, stirring until smooth. Cook, stirring constantly over medium-low heat until thickened. Add cheese, continue cooking just until cheese melts.