Tolerancing plans range in complexity from those in which all parameters are investigated, documented, and controlled, to those that rely solely on whatever quality of optics, mechanical parts, and assemblies is present. The level of complexity desired depends not only on technical considerations but also on cost, schedule, etc. An outline is presented which is applicable not only to the more complex tolerancing plans but also to more modest efforts. The various activities and documents of the complete tolerancing plan are described and illustrated with a view toward clarifying their functions. The outline together with the activities and documents should provide a point of departure for establishing an effective tolerancing plan in a given situation.