Traditionally, parts fabrication in the aerospace and automotive industries has been associated with a number of manufacturing processes. The traditional metrics for assessing competing processes are quality, cost and production rate. Increasingly, however, market driven uncertainties are starting to dominate fabrication process design and selection. Two types of uncertainties are of particular interest: demand fluctuations and part specification changes. This book surveys flexibility strategies and practices that allow enterprises to quickly and cost effectively respond to changes in both demand and specification. The literature on parts fabrication flexibility is thoroughly reviewed and the discussion is augmented with data and interviews obtained from a number of companies. A simple case study is worked out in order to illustrate the fundamental metrics and mathematics involved in assessing parts manufacturing flexibility. It is shown that production volume remains an important ingredient of any flexibility strategy, leading to different regimes for the aerospace and automotive industries.