Final answer:
The exact form a contractor or salesperson must attach is not specified, but it is generally a form relevant to the contract such as a change order form or certification, depending on the specifics of the business and legal requirements.
Step-by-step explanation:
The contractor or salesperson must attach to the signed contract two copies of a separate completed form titled something specific to their business dealings, which is not mentioned clearly in the provided text. In general, such a form might be a change order form, a certification of performance, a receipt of notice, or a disclosure agreement, depending on the nature of the contract and the requirements of the applicable law or regulations. Without additional context, however, it is not possible to provide the exact title of the form that must be attached.