Traditional security measures must increasingly be integrated with bullet- and attack-resistant physical barrier systems. Designing such barrier systems begins by understanding the differences between material and system certification. As physical barriers become more widely used, more information is needed on proper system design and on standardization in the certification process. This information, however, is hard to find because the use of certified systems has traditionally been minimal. Furthermore, product information available to security practitioners is market-driven, and various and often conflicting testing and certification formats exist in the bullet- and attack-resistant product market. Before purchasing a physical barrier system, security managers must understand key components of a certified system: available level of protection, different testing formats, qualified independent laboratories, performance characteristics of different raw materials (transparent and opaque), and common design considerations (application, cost, product performance, and manufacturer performance). The systems- based approach to designing, specifying, and certifying bullet- and attack-resistant physical barriers continues to gain popularity. Models for a systems-based approach, such as the one developed by the State Department for U.S. embassies, are becoming benchmarks for government, commercial, and private applications nationwide.