A more thorough explanation:

A rewritten specification is a detailed statement that describes the measurements, quality, materials, or other items to be provided under a contract. It can also refer to the part of a patent application that describes how an invention is made and used, the best mode of operation of the claimed invention, and the inventor's claims.

For example, if a company wants to build a new office building, they will create a specification that outlines the size of the building, the materials to be used, and the quality of the work. This specification will be used to ensure that the building is constructed according to the agreed-upon standards.

In the case of a patent application, the specification must be clear and complete enough to enable a person of ordinary skill in the art to make and use the invention. It must also disclose the best mode of working the invention. For instance, if someone invents a new type of phone, they will need to provide a detailed specification that explains how the phone works and how it is different from other phones on the market.

Occasionally, a specification may need to be rewritten or replaced. This can happen if the original is illegible or unreadable, or if amendments need to be made. In this case, a substitute specification can be created, which must be accompanied by a statement that it contains no new matter and a copy showing what has been added and deleted since the original specification.