Theories and practical skills for use in optical shops are presented in this rate training manual, prepared for regular navy and naval reserve personnel. Light theories are analyzed in connection with mirrors, prisms, lenses, and basic optical systems. Following fundamentals of mechanical design and construction, maintenance procedures are studied to give a general knowledge of optical repair. Special descriptions are made of such instruments as spyglasses, telescopes, magnetic compasses, azimuth and bearing circles, sextants, stadimeters, telescopic alidades, binoculars, submarine periscopes, and night vision sights. To give enough background for readers, operations of lathes, grinders, milling machines, and drill presses are also discussed. Besides illustrations for explanation purposes, information on the opticalman rating structure is also provided.