The lockup on a S&W revolver is at the front and rear of the extractor rod, and even a slightly bent one can cause difficulty in lockup. The Brownells Yoke/Crane Alignment Tool enables a gunsmith to more easily and precisely align the crane in a matter of minutes without "guesswork". Precision ground and hardened to within .0005" on all critical dimensions. Full instructions come with each tool. These Yoke/ Crane Alignment Tools are hardened to Rc 52-54 to maintain exact specs. The #1 alignment tool is for use with the S&W J Frame (Centerfire models only), and the #2 alignment tool is for use with the S&W K, L, and N frames.