Publisher Summary Plot plans, foundation-location drawings, and equipment-location drawings are developed using the plant coordinate system. Universally recognized throughout the piping industry, the plant coordinate system uses intersecting grid lines, similar to the Cartesian coordinate system, to locate buildings, structures, foundations, equipment, and piping configurations. Unit plot plans highlight the location of all the buildings, equipment, pipe racks, and other items of importance in the unit. The purpose of this drawing is not to show detail but rather to depict the arrangement of various components to be erected in the unit. Adequate arrangement and spacing of components within the facility depend on a number of factors, such as piping codes, space availability, worker accessibility, and client preferences. All pieces of mechanical equipment to be installed within the facility are positioned using two intersecting coordinate lines: one north/south and one east/west. These intersecting coordinates define the precise position of the equipment by locating the centerline of its foundation. The piping drawing index is developed from the plot plan. This drawing divides the plot plan into smaller drawing areas using match lines. Match lines are lines drawn and labeled that allow the smaller drawing areas to be pieced together to form the larger plot plan—similar to a puzzle.