When you put the hammer in the safety notch, that piece swings up and is a positive block for the hammer to rest on. It was an effort to make the gun safe to carry with 6 rounds without having to add a transfer bar. It's a good system that Uberti used on several name guns, the Iver Johnson, Navy Arms, and several others. Others had a long cylinder pin that would block the hammer when pushed back into the second notch. This was unhandy and unuseable in the field and was there only to satisfy the lawyers while the hammer lever is a true safety. Enjoy that gun, it's a shooter. 44 Man