This chapter examines the application of the Theory of Constraints (TOC) to production environments. We begin by developing the Drum-Buffer-Rope (DBR) system which emerges through the application of the five focusing steps of TOC to production environments. The basic elements of DBR are presented along with a detailed example which shows the entire process. We then review the Buffer Management (BM) methodology which is a key element in the use of DBR for managing operations. BM provides the control mechanism to DBR as well as valuable input for driving an improvement process. We then present the TOC methodology for the classification of complex production operations. Based on the flow characteristics of the production process this method results in four major types of production operations - V, A, T and I. We close the chapter with a discussion of the classification criteria, the key attributes and operational issues of each type of plant and the guidelines for the application of DBR in each production type.