I just got a used New Model Single Six with and adjustable rear sight. The rear sight blade was missing so I purchased one and for the life of me I cant figure out how to install it. It DOES have the little spring in there and the windage adjustment screw but I can not figure out how to get that blade in there.

Any advise?

Welcome to the forum Whammo. Rules are simple, be nice and join in.

You might give Ruger a call and ask them. It's been a while since I fiddled with a single action Ruger sight. You also could give Brownell's tech section an email or a call they can be really helpful in situations like that.