1. An old bird is not to be caught with chaff.
2. Old birds are not to be caught with chaff.
3. Mr Smith is a shrewd man, he is not to be caught with chaff.
4. Frederick the Great was too old a bird to be caught with chaff.
5. Mr Adams is a shrewd man, he is not to be caught with chaff.
6. He is not a child. I don't think he will be caught with chaff.