Some of the most important operations and maintenance (O&M) documentation products of a construction project are the as-built drawings. As-built drawings are usually the original design drawings revised to reflect any changes made in the field (e.g., design changes issued by change order, component relocations required for coordination, and rerouting of distribution systems).

A standard, though by no means the only, approach to as-built drawing preparation is for the installation contractors to maintain a master set of manually marked-up "red-line" record drawings in the construction trailer.