The Full Form of COW is Clerk of Works.

The Clerk of Works (or Clerk of the Works), often abbreviated CoW, is employed by an architect or a client on a construction site. The role is primarily to represent the interests of the client in regard to ensuring that the quality of both materials and workmanship are in accordance with the design information such as specification and engineering drawings, in addition to recognized quality standards. The role is defined in standard forms of contract such as those published by the Joint Contracts Tribunal. “Clerks of works” are also the most highly qualified non-commissioned tradesmen in the Royal Engineers. The qualification can be held in three specialisms: electrical, mechanical and construction.

Historically, the Clerk of Works was employed by the architect on behalf of a client, or by local authorities to oversee public works. The CoW can also be employed by the client (state body/local authority/private client) to monitor design and build projects where the traditional role of the architect is within the design and build project team.

Maître d’oeuvre (master of work) is a term used in many Francophone jurisdictions for the office that carries out this job in major projects; the Channel Tunnel project had such an office. In Italy, the term used is direttore dei lavori (manager of the works).