This document, focuses on the critical importance of diagnosing failure modes in bolts for effective root cause analysis (RCA). It emphasizes that accurate failure mode diagnosis, often achievable through visual examination with proper training, is a crucial first step in any RCA to prevent recurrence. While acknowledging the value of expert lab analysis, the guide outlines common bolt failure modes readily identifiable through visual inspection. The document summarizes common causes of bolt failure and describes methods for diagnosing these failure modes, providing practical guidance for improving RCA processes and preventing future failures.