Guide Line to prepare Hook- Up drawings for Field Instrument.
An Instrument Index is a super starting point for any design, it is really a database of all the necessary references which are required in an instrument design.

Tag number, Numbers of the loop drawing, Layout & routing drawing and isometric piping drawing containing the particular control loop component.
Elevations of both the primary control loop component and process connection.
Tagging of mechanical (piping or equipment) to instrumentation interface
Tagging of all elements/fittings & valves with item numbers.
Direction of slopes in hook-up lines.
Elevation of Instrument.
Maximum allowable lengths of hook-up lines.
Accessories often detailed include Monoflanges, Double Block and Bleed Valves and Fittings etc.
Material take off with part numbers, number of particular fittings, size, connection, material type, mounting type.
weather shield and tubing specification