What?
Did you get a whole sight? or a sight blade?
The single six and mark I & II sights have a screw hole in them. They are screwed onto the barrel. Screw hole is in the top of the base behind the blade.
Most blackhawk sights are one piece and are soldered on.
Most super blackhawk sights are two piece. Base is soldered onto the barrel. Blades are held in place with a roll pin thru the side of the base, thru the blade, and into the opposite side of the base.
What did you have? What did you get?
Better clarify or take to gunsmith.
Steve
