Abstract Careful installation of instruments in airplanes is most essential in order that they function properly, and remain free from trouble. The author describes details of installation that have proved satisfactory for the principal types, and points out certain things that should be avoided. Service work on instruments is divided into two classes, periodic overhauling and inspection, and adjustments done at service stations. Engineering service to the airplane builder is considered a very important part of the instrument manufacturer’s duties as it insures proper installation of the product.