A more thorough explanation:

Definition: A shingle is a small sign that is usually placed on the door of a professional's office, especially a lawyer's office. It is a dignified way of marking the office and letting people know who works there.

Example: The lawyer's shingle read "John Smith, Attorney-at-Law" and was placed on the door of his office.

Explanation: In this example, the shingle is a small sign that is placed on the door of a lawyer's office. It lets people know that John Smith is an attorney and works in that office. The shingle is a professional way of marking the office and advertising the services offered.

Example: The doctor's shingle read "Dr. Jane Doe, MD" and was placed on the door of her clinic.

Explanation: In this example, the shingle is a small sign that is placed on the door of a doctor's clinic. It lets people know that Dr. Jane Doe is a medical doctor and works in that clinic. The shingle is a professional way of marking the clinic and advertising the medical services offered.