Prequalified welding procedures are trusted because they are built on strict, code-defined requirements that intentionally eliminate conditions most likely to compromise weld quality. This article explains why AWS D1.1 allows prequalification without testing and how its limitations—such as prohibiting short-circuit transfer, narrow groove angles, inadequate preheat, and certain joint configurations—are designed to prevent lack of fusion, cracking, and other defects. Each restriction has a clear technical purpose rooted in weld soundness and repeatability. When all prequalification rules are followed, a WPS can be written and used in production quickly while still providing reasonable assurance of quality. As with any procedure, welder qualification remains essential to ensure acceptable welds are consistently produced.