Specifiers should not include unnecessary restrictions on how to achieve the results. Use of proprietary information provides the specifier the greatest control over product selection. This method is the simplest and shortest to write. As with the descriptive method, the burden of performance of the specified products rests with the specifier, and this method limits competition. For this reason, proprietary specifications are often prohibited on public-funded projects.
Proprietary specifications can be open or closed.
Open proprietary specifications are used to allow the consideration of substitution requests, and closed proprietary specifications are used if substitutions are prohibited. Nonrestrictive proprietary specifications include the use of proprietary information to set a level of quality by which other products are judged when substitutions are proposed. This requires rules about how other products will be evaluated, who will evaluate and decide, and how decisions will be documented. These rules are generally included in Division 1 specifications. The function of specifications is to define the quality of products, materials, and workmanship.