The lockup mechanism on an S&W revolver is located at the front and rear of the extractor rod. Even a slightly bent rod can lead to lockup issues. The Brownells yoke/crane alignment tool allows gunsmiths to align the crane with greater ease and precision, eliminating guesswork and completing the task in minutes. The tool is precision-ground and hardened to within 0.0005 inches on all critical dimensions. Each tool is accompanied by comprehensive instructions. These yoke/crane alignment tools are hardened to Rc 52-54 to ensure exact specifications are maintained. The #1 alignment tool is specifically designed for use with the S&W J Frame (centerfire models only).