This listing is for a vintage solid brass ball in hand door knocker.  The whole piece is a little under 5 inches in length.  It weighs 1 pound, 2.7 ounces.

I'm unaware of what thread count is needed for the screw to install.  It does not come with any installation hardware.

The door knocker is in good condition overall.  It has light wear and I'm uncertain whether it was used in the past.  Please see photos.