This is a Joist Brace made by an employee of Oak Harbor Boat Works from an old brace I gave him by cutting the palm pad and handle from the old brace and bending and brazing the components together to make the tool.  Probably much like the first joist brace which was made to work in the spaces between joists.  I have used both a regular brace and a joist brace and there is no comparison for dealing with fasteners.  The Joist Brace wins hands down.