Since you have to break the existing windage bolt to get the blade out S&W sells a rear sight blade kit that includes the windage bolt and nut. Instructions are in 500 Magnum Nut's Frequently Asked Questions sticky thread in S&Wsmithing: FAQ's While he suggests buying a small spanner wrench one can easily be made by filing a small flat head screw driver. Be careful to not loose the tiny detent plunger and its spring. Those two parts love to pup out and hide in your carpet. Brownell's is an alternate source for the kits and they sell the spanner.