Useful tools don' t have to be expensive! This handy bracket slides over the sprocket shaft splines of big twin engines, and bolts to one of the primary bolt holes of the crankcase to keep the crank from rotating. Like an extra set of hands while installing pistons and cylinders, or any other operation where you don"t want the crank to turn. Works on 1970-up Harley-Davidson big twins. S&S Part #: 50-9870